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Updates in TB

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Page 1: Updates in TB

An overview and Updates in TB

By

Gamal Rabie Agmy MD FCCP Professor of Chest Diseases Assiut University

ERS National Delegate of Egypt

The increasing prevalence of

tuberculosis in both immunocompetent

and immunocompromised individuals

in recent years makes this disease a

topic of universal concern

Introduction

The World Health Organization (WHO) estimates that each year more than 8 million new cases of tuberculosis occur and approximately 3 million persons die from the disease

Ninety-five percent of tuberculosis cases occur in developing countries

It is estimated that between 19 and 43 of the worlds population is infected with Mycobacterium tuberculosis the bacterium that causes tuberculosis infection and disease

Epidemiology

Epidemiology

Most cases in the US are due to

reactivation especially amongst immigrants

Highest risk of progression to active TB is within 2 years of seroconversion

Increase in incidence in late 1980s-early 90s

largely due to HIV

Needs to be reported to the health

department

Microbiology

Aerobic

Bacillus (rod-shaped)

Non-spore forming

Non-motile

Cell wall ndash mycolic acid ndash retains acid fast

stain

Growth - doubling time of 15-20 hrs

3-8 weeks for growth on solid media

TB Skin Testing

PPD ndash purified protein derivative of tuberculin (antigenic)

Delayed type hypersensitivity reaction

PPD may not become ldquopositiverdquo until 3 months after exposure

Boosting effect

Skin Test Interpretation

PPD gt= 5 mm ndash HIV patients

ndash Recent contacts of someone with TB

ndash Fibrotic changes on CXR cw prior TB

ndash Organ transplant recipients

ndash Immunosuppressed (includes patients receiving the equivalent of 15 mgday or more of prednisone for one month or more)

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 2: Updates in TB

The increasing prevalence of

tuberculosis in both immunocompetent

and immunocompromised individuals

in recent years makes this disease a

topic of universal concern

Introduction

The World Health Organization (WHO) estimates that each year more than 8 million new cases of tuberculosis occur and approximately 3 million persons die from the disease

Ninety-five percent of tuberculosis cases occur in developing countries

It is estimated that between 19 and 43 of the worlds population is infected with Mycobacterium tuberculosis the bacterium that causes tuberculosis infection and disease

Epidemiology

Epidemiology

Most cases in the US are due to

reactivation especially amongst immigrants

Highest risk of progression to active TB is within 2 years of seroconversion

Increase in incidence in late 1980s-early 90s

largely due to HIV

Needs to be reported to the health

department

Microbiology

Aerobic

Bacillus (rod-shaped)

Non-spore forming

Non-motile

Cell wall ndash mycolic acid ndash retains acid fast

stain

Growth - doubling time of 15-20 hrs

3-8 weeks for growth on solid media

TB Skin Testing

PPD ndash purified protein derivative of tuberculin (antigenic)

Delayed type hypersensitivity reaction

PPD may not become ldquopositiverdquo until 3 months after exposure

Boosting effect

Skin Test Interpretation

PPD gt= 5 mm ndash HIV patients

ndash Recent contacts of someone with TB

ndash Fibrotic changes on CXR cw prior TB

ndash Organ transplant recipients

ndash Immunosuppressed (includes patients receiving the equivalent of 15 mgday or more of prednisone for one month or more)

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 3: Updates in TB

The World Health Organization (WHO) estimates that each year more than 8 million new cases of tuberculosis occur and approximately 3 million persons die from the disease

Ninety-five percent of tuberculosis cases occur in developing countries

It is estimated that between 19 and 43 of the worlds population is infected with Mycobacterium tuberculosis the bacterium that causes tuberculosis infection and disease

Epidemiology

Epidemiology

Most cases in the US are due to

reactivation especially amongst immigrants

Highest risk of progression to active TB is within 2 years of seroconversion

Increase in incidence in late 1980s-early 90s

largely due to HIV

Needs to be reported to the health

department

Microbiology

Aerobic

Bacillus (rod-shaped)

Non-spore forming

Non-motile

Cell wall ndash mycolic acid ndash retains acid fast

stain

Growth - doubling time of 15-20 hrs

3-8 weeks for growth on solid media

TB Skin Testing

PPD ndash purified protein derivative of tuberculin (antigenic)

Delayed type hypersensitivity reaction

PPD may not become ldquopositiverdquo until 3 months after exposure

Boosting effect

Skin Test Interpretation

PPD gt= 5 mm ndash HIV patients

ndash Recent contacts of someone with TB

ndash Fibrotic changes on CXR cw prior TB

ndash Organ transplant recipients

ndash Immunosuppressed (includes patients receiving the equivalent of 15 mgday or more of prednisone for one month or more)

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 4: Updates in TB

Epidemiology

Most cases in the US are due to

reactivation especially amongst immigrants

Highest risk of progression to active TB is within 2 years of seroconversion

Increase in incidence in late 1980s-early 90s

largely due to HIV

Needs to be reported to the health

department

Microbiology

Aerobic

Bacillus (rod-shaped)

Non-spore forming

Non-motile

Cell wall ndash mycolic acid ndash retains acid fast

stain

Growth - doubling time of 15-20 hrs

3-8 weeks for growth on solid media

TB Skin Testing

PPD ndash purified protein derivative of tuberculin (antigenic)

Delayed type hypersensitivity reaction

PPD may not become ldquopositiverdquo until 3 months after exposure

Boosting effect

Skin Test Interpretation

PPD gt= 5 mm ndash HIV patients

ndash Recent contacts of someone with TB

ndash Fibrotic changes on CXR cw prior TB

ndash Organ transplant recipients

ndash Immunosuppressed (includes patients receiving the equivalent of 15 mgday or more of prednisone for one month or more)

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 5: Updates in TB

Microbiology

Aerobic

Bacillus (rod-shaped)

Non-spore forming

Non-motile

Cell wall ndash mycolic acid ndash retains acid fast

stain

Growth - doubling time of 15-20 hrs

3-8 weeks for growth on solid media

TB Skin Testing

PPD ndash purified protein derivative of tuberculin (antigenic)

Delayed type hypersensitivity reaction

PPD may not become ldquopositiverdquo until 3 months after exposure

Boosting effect

Skin Test Interpretation

PPD gt= 5 mm ndash HIV patients

ndash Recent contacts of someone with TB

ndash Fibrotic changes on CXR cw prior TB

ndash Organ transplant recipients

ndash Immunosuppressed (includes patients receiving the equivalent of 15 mgday or more of prednisone for one month or more)

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 6: Updates in TB

TB Skin Testing

PPD ndash purified protein derivative of tuberculin (antigenic)

Delayed type hypersensitivity reaction

PPD may not become ldquopositiverdquo until 3 months after exposure

Boosting effect

Skin Test Interpretation

PPD gt= 5 mm ndash HIV patients

ndash Recent contacts of someone with TB

ndash Fibrotic changes on CXR cw prior TB

ndash Organ transplant recipients

ndash Immunosuppressed (includes patients receiving the equivalent of 15 mgday or more of prednisone for one month or more)

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 7: Updates in TB

Skin Test Interpretation

PPD gt= 5 mm ndash HIV patients

ndash Recent contacts of someone with TB

ndash Fibrotic changes on CXR cw prior TB

ndash Organ transplant recipients

ndash Immunosuppressed (includes patients receiving the equivalent of 15 mgday or more of prednisone for one month or more)

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 8: Updates in TB

Skin Test Interpretation

PPD gt= 10 mm ndash Recent immigrants (lt 5 years) from high

prevalence areas (Eastern Europe Latin America Asia Africa)

ndash IV drug users

ndash Residents and employees of high risk facilities (hospitals nursing homes homeless shelters prisons)

ndash Children lt 4 years of age

ndash Mycobacteriology lab personnel

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 9: Updates in TB

Skin Test Interpretation

PPD gt= 10 mm

ndash People with medical conditions that place

them at high risk for active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 10: Updates in TB

Skin Test Interpretation

PPD gt= 15 mm

ndash Low risk people

ndash Routine tuberculin testing not

recommended for low risk populations

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 11: Updates in TB

Skin Test Intrepretation

False positives ndash Non-tuberculous mycobacterial infection

ndash BCG vaccination

False negatives ndash HIV

ndash Malnutrition

ndash Steroid therapy

ndash Recent infection

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 12: Updates in TB

BCG

Bacille Calmette-Guerin vaccination Live attenuated mycobacterial strain derived

from M bovis

Can yield false positives to PPD ndash less likely

as time from vaccination increases

Reactions gt 20 mm likely are true

CDC advises that the PPD be interpreted by the same guidelines (ignore the BCG history)

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 13: Updates in TB

Quantiferon Testing

Whole blood in vitro test ndash Lymphocytes release IFN gamma in

presence of 2 TB antigens

Will be positive in latent or active TB

Advantages ndash No error in interpretation

ndash No follow-up in 48-72 hours

ndash No boosting

ndash Not affected by BCG

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 14: Updates in TB

Quantiferon Testing

Disadvantages ndash Must be processed within 12 hours of

collection

ndash False + with atypical mycobacteria

ndash Too many indeterminate results with current version (Q-Gold)

ndash May be less reliable in pregnant women children and immunocompromised

ndash Does not distinguish between active and latent TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 15: Updates in TB

Causative organism Mycobacterium tuberculosis COMPLEX

Stained with

-Modified gram stain gram positive

-Carbolfuchsin stain Cold method(Kynon)

Hot(Zeil-Neelson)

- Fluorescent dyes rhodamine and

auramine stains

Bacteriology

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 16: Updates in TB

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 17: Updates in TB

Zeil-Neelson Staining

Wire 001 ml of specimen 200mm2 slide

Oil immersion field 002mm

Slide=10000 field=001ml specimen

10000 organismslide=1 AFBfield=1000000 organismml

1000 organismslide=1 AFB10 field=100000 organismml

100 organismslide=1 AFB100field=10000 organismml

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 18: Updates in TB

QUANTITATION SCALE FOR ACID-FAST BACILLUS

SMEARS ACCORDING TO STAIN USED

Carbolfuchsin (times 1000) Fluorochrome

(times 250) Quantity Reported

No AFB300 fields No AFB30 fields No AFB seen

1-2 AFB300 fields 1-2 AFB30 fields Doubtful repeat

test

1-9 AFB100 fields 1-9 AFB10 fields Rare (1+)

1-9 AFB10 fields 1-9 AFBfield Few (2+)

1-9 AFBfield 10-90 AFBfield Moderate (3+)

gt 9 AFBfield gt 90 AFBfield Numerous (4+)

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95

Antibody detection by ELISA 1048708 The detection of mycobacterial

antigens by immunoassay in clinical specimens with

high amp variable

protein content is difficult

1048708 Detection in sputum presents even

greater clinical problem because sputum is a non-

homogenous gel

1048708 False positive rates are high

1048708 Abandonment of this diagnostic tool

Insta test TB 1048708 It is a rapid in vitro assay for the

detection of antibody in active TB disease using whole blood or

serum

1048708 The test employs an Ab binding protein

conjugated to a

colloidal gold particle and a unique combination of TB

Ags immobilized on the membrane Tuberc Lung Dis 19982 541

TB MPB 64 patch test 1048708 MPB 64 is a specific mycobacterial

antigen for Mtb complex

1048708 This test becomes +ve in 3-4 days

after patch application

and lasts for a week

1048708 Specificity~100 Sensitivity~981 1048708 This promising test has been reported

so far only in one

setting in Philippines and needs to be

carried out in other

settings Ind J Tuberc Lung Dis 19982 541

Quantiferon-GOLD 1048708 Due to advances in molecular biology

and genomics an alternative has emerged for the first time in

the form of a

new class of in vitro assays that measure

interferon

(IFN-γ) released by sensitized T cells after stimulation by

M tuberculosis antigens

1048708 Measures immune reactivity to

Mtb

Quantiferon-GOLD 1048708 Interferon-γ assays measure cell-

mediated immunity by quantifying IFN-γ released from

sensitized T cells

in whole bloodPBMCs incubated with TB

antigens

QuantiFERON-TB reg test (Cellestis

Australia

ndash Commercially available

ndash Measures amount of IFN-γ produced

(ELISA) ndash FDA-approved for the detection of LTBI

2001

1048708 ELISPOT assay (Oxford UK)

ndash Similar to QFT

ndash Measures number of reactive lymphocytes

ndash Not commercially available

Early assays employed PPD (same

specificity problems

as the TST)

1048708 Newer assays (eg QFT-Gold) employ

TB-specific antigens ESAT-6 and CFP-10

1048708 Proteins encoded within the region of

difference 1 of

Mtuberculosis 1048708 Not shared with the BCG sub-strains and most NTM

(except M kansasii M szulgai M marinum and nonpathogenic Mbovis)

Quantiferon-GOLD

Improved specificity able to distinguish

between TB and

NTM BCG infection

1048708 Studies in contacts HIV infected and

children underway 1048708 Recommended for use in ldquoALL

circumstances in which the

tuberculin skin test is currently usedrdquo

1048708 Includes contact investigations

immigrant evaluation surveillance (eg healthcare workers) Mazurek et al MMWR 20055415

Quantiferon-GOLD

IGRAs Vs TST 1048708 TST

1048708 In vivo 1048708 Single antigen

1048708 Boosting

1048708 2 patient visits

1048708 Inter-reader variability

1048708 Results in 2-3 days 1048708 Read in 48-72 hrs

1048708

IGRAs

1048708 In vitro 1048708 Multiple antigens

1048708 No boosting

1048708 1 patient visit 1048708 Minimal inter-reader

variability

1048708 Results in 1 day

1048708 Stimulate wi 12 hrs

IGRAs Vs TST 1048708 QFT-g vs TST Agreement = 836

1048708 Factors associated with discordance ndash Prior BCG

ndash Non-tuberculous mycobcateria immune

reactivity

ndash Site bias in reading TST

ndash TB Treatment Mazurek et al JAMA 20012861740

Biochemical markers of

Diagnosis 1048708 Adenosine deaminase (ADA)

1048708 Bromide partition test

1048708 Gas chromatography of mycobacterial

fatty acids (Tuberculostearic acid)

Adenosine Deaminase (ADA) 1048708 It is an enzyme of purine metabolism

The level of this enzyme is 10 times higher in lymphocytes

(T cells gtB

cells) than in RBC

1048708 Whenever there is cell mediated

immune response to an antigenic stimuli the ADA levels are the

highest

1048708 ADA is measured by the colorimetric

method of Giusti

enzymatic reaction is Adenosine + H2O + ADA = Inosine + NH3

+ADA

1048708 The amount of ammonia liberated

is measured by

the colorimetric method Cut-off Sensitivity Specificity

Pleural Fluid 50 IUml 95 100

Ascitic Fliud 323 IUml 89 98 CSF 9 IUml 100 100

Bromide Partition Test 1048708 The partition of bromide ion between

serum and CSF after a loading dose reflects the integrity of

the blood

brain barrier

1048708 Either by direct chemical measurement

or by using an isotopic tracer the ratio of bromide in

serum to that in

CSF can be estimated

1048708 Values lt16 are characteristic of TBM

In different studies the sensitivity and

specificity of this

test has been found to be near 90

1048708 It may be false +ve in herpes simplex

listeria mumps measles pyogenic meningitis and

hypothyroidism

1048708 With the availability of better tests this

test has been

given up Taylor J et al J Clin Microbiol 1999 34 56-59

Tuberculostearic Acid (TBSA) 1048708 TBSA is found in the cell wall of

mycobacterium 1048708 It is identified by gas chromatography

or mass

spectrophotometry

1048708 It is a costly investigation and requires

complex analytical equipment (Seldom used)

1048708 Sensitivity gt95Specificitygt99

French M et al J Clin Microbiol 1998 54 987-990

CT Scan and MRI Scan in the

diagnosis of TB 1048708 The advent of CT and MRI imaging in

the last two

decades has redefined the approach in

analysis of various diseases including TB

1048708 CT and MRI have shown several

advantages over

conventional radiology in early diagnosis

and follow-up of TB in different parts of the body

Buxi TBS Indian J Pediatr 200269965-972

Pulmonary TB

1048708 Lobar Pneumonia 1048708 CT is superior than plain CXR in picking

up the

consolidation atelectasis and the hilar LN

thereby making the diagnosis easy

1048708 MRI reveals some of these changes

however CT is

the diagnostic modality of choice in such

cases

1048708 Bronchopneumonia 1048708 On CT it is usually BL and widespread

not always

symmetrical involvement of lungs

Hilar and Mediastinal

Lymphadenopathy 1048708 CT and MRI depict the hilar and

mediastinal LN

equally well

1048708 Calcification in the nodes is however

better seen on CT

1048708 Necrosis is seen as focal areas of low

attenuation on

a CECT

1048708 On MRI focal necrosis is seen as areas of increased

signal intensity on T2W images

1048708 EBTB 1048708 HRCT is sensitive in the detection of

early

endobronchial spread of disease

Miliary TB

1048708 Earliest form of miliary TB is detectable

on HRCT

1048708 Coalescing nodules result into patchy

irregular opacities and HRCT shows this variation

effectively

and has been described as ldquosnowstorm

appearancerdquo

1048708 HRCT shows cavitation which is not evident on plain

CXR

1048708 Pleural Effusion

1048708 CT is sensitive to diagnose and define

even minimal pleural effusionpleural calcification

1048708 Pleural fluid is seen on inversion

recovery MR

images as areas of increased signal

intensity along the inner aspects of the chest wall

Skeletal TB

1048708 Pottrsquos Disease (vertebral TB) 1048708 CT and MRI helps in demonstrating a

small focus of

vertebral body involvement and defining

the extent of the disease

1048708 CTMRI help to evaluate TB involving

the craniovertebral

junction sacro-iliac joint and posterior

appendages 1048708 They are also helpful in assessment of

spinal canal

encroachment posterior element

involvement and in

deciding the surgical approach

GIT TB

1048708 Strictures of the small bowel mucosal

edema and

thickening are well visualized on CT 1048708 MRI depicts the para-aortic aortocaval

and

mesentric lymph nodes effectively 1048708 GUT TB

1048708 Various patterns of hydronephrosis may

be seen

at MR urography

1048708 MRI helps to differentiate macronodular

TB lesions from the other mass lesions

Boehme C NEJM 2010

CXR Findings

Primary TB Lower or middle lobe infiltrates

Reactivated TB Apical infiltratescavitation

Latent TB Usually normal

Nodules in hilar area or upper lobes

Pleural scarringthickening

Transmission

Transmitted by airborne particles 1-5 microns in size

Ease of transmission depends on duration and proximity of contact as well as the number of bacteria excreted

Infection can result from only 1-5 bacteria entering a terminal alveolus

Only those with active pulmonary TB are infectious

M tuberculosis is transmitted via airborne

droplet nuclei that are produced when

persons with pulmonary or laryngeal TB

cough sneeze speak or sing

Droplet nuclei may be produced by aerosol

treatments sputum inductionaerosolization

during bronchoscopy and through

manipulation of lesions or processing of

tissue or secretions in the hospital or

laboratory

Pathogenesis

ndash Inhalation -gt phagocytosis by alveolar macrophages

ndash Bacterial multiplication occurs intracellularly

ndash Lymphatic spread to regional lymph nodes or

hematogenous dissemination

ndash Immune response results in granuloma formation (containment of infection)

ndash Cell death in the granuloma results in caseous

necrosis

ndash Bacteria can remain dormant in the granuloma

Pathogenesis

ndash Medical conditions that increase risk for

active TB

Chronic renal failure

Diabetes mellitus

Silicosis

Leukemiaslymphomas

Carcinoma of the headneck or lung

Weight loss gt 10 of ideal body weight

Gastrectomyjejunoileal bypass

Primary pulmonary tuberculosis

The first infection with tubercle bacillus

Includes the involvement of the draining

lymph nodes in addition to the initial

lesion(Ghon)

Clinical features

Majority symptomless(specially in

young adults)

Brief febrile illness

Loss of appetite

Failure to gain weight in children

Cough is not unusual and may mimic

paroxysm of whooping cough

Physical signs

bullMay be normal

bullCrepitation may be heard

bullPrimary lesion could be

heard

bullSegmental or lobar collapse

may occur

Radiological features bullLymphadenoathy hilar lymph nodes

are most commonly involved rarely

paratrachealCalciflcation of the nodes

may occur

bull Pulmonary componant ( mainly in

adults) segmental or lobar

consolidation or obstructive

emphysema

bullResolution of radiological shadow 6m-

2ys

Diagnosis Vague ill health with history of contact

X-ray

Tuberclin test is usually strongly

positive

Sputum and gastric lavage for direct

smear and culture helpful in 20-25 of

cases

DNA amplification PCR

Post primary pulmonary tuberculosis

The most important type of tuberculosis

because it is the most frequent and

smear positive sputum is the main

source of infection responsible for the

persistence of the disease in the

community

Source

1 Direct progression of the primary

lesion

2 Reactivation of the quiescent primary

or post primary

3 Exogenous infection

Predisposing factors for reactivation

1 Malnutrition

2 Poor housing and overcrowding

3 Steroid and other immunosuppressive

drugs

4 Alcoholism

5Other diseases HIV malignancy

lymphomas LeukaemiaDiabetes

Clinical features

Mainly in middle aged and elderly

A-Symptoms 1 May be no symptoms or just mild debility

Gradual onset of symptoms over weeks or months

2 General malaise

3 Loss of appetite loss of weight

4 Febrile course

5 Night sweating

6 Cough with or without sputum

7 Sputum could be mucoid purulent or blood stained

8 Could be presented with frank haemoptysis

9 Tuberculous pneunonia

B-Signs 1 May be no signs

2 Pallor cachexia

3 Fever

4 Post tussive crepitations on the apices

5 Signs of Consolidation

6 Signs of fibrosis

7 Signs of cavitary lesion

8 Localised wheezes in endobronchial

tuberculosis

Lymph nodes Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

3 3

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

6 5

Lymph nodes

Anatomic Considerations

Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac

7

7

8

9

Radiology 1 Bilateral upper zone fibrotic shadows with

shift of trachea mediastinum distortion of

fissures and diaphragm and elevation of the

pulmonary hila

2 Soft confluent shadows of exudative lesion

(DD pneumonia)

3 Calcification

4 Cavitation

5 Tuberculoma

6 Hilar and paratracheal lymph node

enlargement may be present

Radiological classification 1Minimal slight or moderate opacity No

cavity Extent not more than space

above 2nd costocondral junction

2 Moderately advanced In one or both

lungs slight or moderate opacity extent

equivalent to volume of one lung Dense

confluent shadow equivalent to one third

the volume of one lung Diameter of

cavities not more than 4 cm

3 Far advanced

Any lesiongtthe moderately advanced

Diasnosis 1) Clinical

2) Plain X-ray

3) Sputum Examination direct smear and culture (very

important)

4) Other samples Gastric aspirate laryngeal swab fiberoptic

specimens (washbrushbiopsy)transtracheal spirate

5 Polymerase chain reaction)

6) Tuberclin test mainly strongly positive

7) Others

White blood cells if normal favour the diagnosis

ESR may be elevated

Normocytic normochromic anaemia

CT may be useful in detecting small cavities

or calcification

Miliary Tuberculosis

Produced by acute dissemination of tubercle

bacilli via the blood streamThe term miliary

derives from the radiological picture of

diffuse discrete nodular shadows about the

size of millet seed (2mm)

A- Classical form Clinical features Most common in infants and young children with acute

or subacute febrile illness

In adults the onset is insidious gradual vague ill health

Malaise Cough (usually dry) dyspnea Night sweat is

less common

Headache suggest associated tuberculous meningitis

Chest examination is free crepitations may be found

Hepatomegaly splenomegaly lymphadenopathy

neck rigidity may be found in rare cases

Diasnosis 1) Clinical

2) Xray

3) Choroidal tubercles in fundus examination

4) Tuberclin test not conclusive

5) Direct smear and culture of sputum if

present

6) Other samples as transtracheal aspirate

fiberoptic specimens may be obtained

7) If failed to prove therapeutic trial for 2

weeks

Mycobacterium tuberculosis-latent bacilli are microorganisms that adapt to stressful conditions generated by the infected host against them

By slowing metabolism or becoming dormant they may counterbalance these conditions and appear as silent to the immune system

Moreover the dynamic turnover of the infected cells provokes a constant reactivation of the latent bacilli when the environmental conditions are favourable or an activation after being dormant in necrotic and fibrotic lesions for a long period of time

Achalasia of

esophagus

bull Inhomogeneous

cardiac density

Right half more

dense than left

bull Density crossing

midline (right black

arrow)

bull Right sided inlet to

outlet shadow

bull Right para spinal line

(left black arrow)

bull Barium swallow

below Dilated

esophagus

Dissecting Aneurysm

Mediastinal widening

Inlet to outlet shadow

on left side

Retrocardiac Intact

silhouette of left heart

margin

Pulmonary artery

overlay sign Density

behind left lower lobe

Wavy margin

Treatment

Before 1940s open air (sanatorium)

1946 streptomycin

1952 isoniazid

1970 rifampin

Antituberculous drugs

A First line drugs Isoniazide (INH) or H Rifampicin ( R ) Pyrizinamide ( Z ) Streptomycin ( S ) Ethamutol ( E )

BSecond line drugs Thiacetazone (150mg) Para amino salicylic acid (10-20 g) Ethionamide (lt50Kg 750mgampgt50Kg Ig) Cycloserine 5-20mgKg) Kanamycin Capreomycin Viomycin (20mgKg max Ig)

CNew drugs Amikacin Quinolones Rifabutin new macrolides and Amoxicillin-clavulinic acid

Drugs

Adverse effect

Dose

Dose

Adult

Child

Isoniazide

(INH) or H

5 mgKg up to

12mgKg in

miliary

10 mgKg

Peripheral

neuritis

hepatitis

hypersensitivity

Rifampicin

(R)

lOmg Kg

lt50Kg 450mg

gt50Kg 600mg

10-20mg

Orange urine

Flu like illness

Hepatitis

Hypersensitivity

Blood dyscriasis

Ethambutol

(E)

25mgKg for

two months

then 15mgKg

Contraindi

cated

Retrobulbar

neuritis

Pyrazinamie

(Z)

lt50Kg15g

50-74Kg 2g

gt75Kg 25g

40mgKg

Hepatotoxicity

Hyperuricaemia

Streptomycin

(S)

20mgKg (max

Ig)

20mgKg

Ototoxicity

(vestibular)

Nephrotoxicity

Hypersensitivity

Drus regimens according to WHO guidelines

1-New smear positive patient 2SRHZ6HE(8months regimens)or

2SHE10HE(12months regimens)or

2SRHZ4RH (6 months regimen)

2-Previously treated smear positive patients 2SRHZE1RHZE5RHE (8month regimen) a sensitivity pattern is recommended

3- Smear negative and extrapulmonary TB 2SHE10HE (12 months regimen)

4- Chronic smear positive patient (Treated in

hospital) a Sensitivity pattern is recommended to give

special treatment regimen

Corticosteroid Therapy in Tuberculosis Corticosteroid should never be given to patientswith

tuberculosis unless they are receiving adequate

antituberculous therapy

Indications of steroids

In very ill patient

To control drug hypersensitivity

In tuberculosis of serous sacs (pericarditis peritonitis and

pleural effusion)

In tuberculous meningitis

Addison disease

Genitourinary tuberculosis

Occasionally to suppress lymph node enlargement

Treatment of Active TB

Four drug regimen for first 2 months INH 300 mg

Rifampin 600 mg

PZA 15-30 mgkg

Ethambutol 15-25 mgkg or streptomycin 15 mgkg

Two drug regimen for next 4 months INH and rifampin

If the TB is not resistant (or lt 4 resistance in the community) INH rifampin and PZA for the first 2 months can be used

Treatment of Active TB

INH resistant TB ndash Rifampin PZA and ethambutol for 6

months

Rifampin resistant TB ndash INH PZA and streptomycin for 9 months

or INH and ethambutol for 18 months

MDRXDR TB ndash Based on susceptibility patterns

Blumberg HM IDSA

Factors in Treatment of Latent TB

Age Previously low risk patients older than 35

were not treated ndash higher risk of drug-induced hepatitis

ldquoDecision to tuberculin test is a decision to treatrdquo

Weigh risksbenefits of treatment in low risk patients

Liver disease End stage liver disease and active hepatitis

are relative contraindications to treatment

Treatment of Latent TB

Efficacy of 90 if all the medications are taken

60-70 rates when the drugs are self-administered

Protective effect will last probably for life but at least 20 years

Treatment of Latent TB

Need to exclude active disease before treatment (avoids single drug therapy of active TB)

CXR ndash if changes consistent with TB send

AFB sputum culture

Single drug therapy appropriate for latent TB ndash bacterial load much lower compared with active TB

Treatment of Latent TB

Regimens ndash Isoniazid (INH) daily or twice weekly

under directly observed therapy (esp if adherence is an issue) 9 months of treatment is optimal

At least 6 months is needed

12 months if treatment is interrupted

ndash Rifampin daily 4 months of treatment

Alternative regimen for those exposed to an INH resistant patient

Treatment of Latent TB

Regimens

ndash RifampinPZA for 2 months

Similar in safety and efficacy to 12 month

regimen of INH

No longer recommended due to hepatic toxicity (including liver failure leading to

death)

Treatment of Latent TB

Regimens Multi-Drug Resistant TB

ndash Therapy based on susceptibility pattern of

the index case if information available

ndash 2 drug therapy for 12 months

PZA plus

Ethambutol or

Fluoroquinolone with anti-TB activity

Treatment of Latent TB

If INH treatment is interrupted an additional 3 months should be given

If interruption is gt3 months re-start treatment

If a treated person is re-exposed to someone with TB repeat treatment is not needed unless the patient is HIV+

Treatment ndash Special Situations HIV

Up to 20 of patients with CD4 counts lt 200 can have a normal CXR with active TB ndash send sputum before treatment

Recent contact with someone with active TB treat regardless of PPD result

Anergy testing not recommended

Extrapulmonary TB more common

Immune reconstitution

Same treatment regimens (except rifabutin instead of rifampin for patients on PIs)

Treatment ndash Special Situations

Pregnancy ndash No evidence that PPD testing is harmful

ndash INH not teratogenic hepatotoxicity may be more likely

ndash Rifampin generally considered safe ndash reports of hemorrhage in the newborn

ndash Ethambutol okay

ndash Streptomycin avoid (congenital deafness)

ndash PZA no published safety data

ndash Breast-feeding is not contraindicated

Treatment ndash Special Situations

Pregnancy

ndash Active TB ndash treat

ndash Latent TB (immunocompetent host) ndash

defer therapy until after delivery

ndash Latent TB (HIV or recent converter) ndash immediate therapy with INH

Monitoring on Treatment

INH Side effects Abdominal pain nausea vomiting

Dark urine

Icterus

Easy bruisingbleeding

Arthralgias

Rash

Paresthesiasweakness ndash peripheral

neuropathy is less likely with pyridoxine

Anorexiafatigue

Monitoring on Treatment

INH

ndash Elevated transaminases in 10-20 of

cases ndash especially with EtOH

ndash Should be withheld if transaminases

increase more than 3x the upper limit of normal when associated with symptoms

or 5x the upper limit of normal in

asymptomatic patients

Monitoring on Treatment

Rifampin Side effects

ndash GI upset

ndash Thrombocytopenia

ndash Hepatitis

ndash Flu-like syndrome ndash if taken irregularly

ndash Multiple drug interactions

ndash Orange bodily secretions due to excretion

Monitoring on Treatment

PZA Side effects

ndash GI upset

ndash Hepatitis

ndash Arthralgias

ndash Hyperuricemia ndash acute gout uncommon

Ethambutol

ndash Optic neuritis reversible decreased red-green

color perception and visual acuity

ndash Not hepatotoxic

Adherence

Decreases with duration of therapy whereas efficacy increases with length of treatment

Factors Side effects

Complexity of regimen (active TB)

Perception (especially in latent TB)

Directly Observed Therapy ndash especially in twice weekly regimens

Infection Prevention

If active pulmonary TB is suspected

ndash AFB isolation

ndash Negative pressure

ndash Particulate respirator masks

Isolation not required for

ndash Latent TB

ndash Extrapulmonary TB

Infection Prevention

Isolation can be discontinued

ndash If AFB smears x 3 are negative

ndash An alternative diagnosis is made

If patient has active TB then

ndash After 2 weeks of effective therapy

ndash Resolution of cough fever

ndash Negative or ldquoless positiverdquo AFB smears

S Curve of Golden

When there is a mass adjacent

to a fissure the fissure takes

the shape of an S The

proximal convexity is due to a

mass and the distal concavity

is due to atelectasis Note the

shape of the transverse fissure

This example represents a RUL

mass with atelectasis

Definitions

MDR-TB = Strains resistant to at least INH and RIF (most important 1st-line drugs) XDR-TB = MDR TB strains with additional resistance to any fluoroquinolone and any of the 3 injectable second-line drugs (amikacin kanamycin capreomycin) TDR XXDR = Resistance to all drugs (not standardised defin)

MDR TB XDR TB TB with any

drug

resistance

TDRXXDR TB

204

1st-line

oral

bullINH

bullRIF

bullPZA

bullEMB

bull(Rfb)

Injectables

bullSM

bullKM

bullAMK

bullCM

Fluoroquinolones

bullCipro

bullOflox

bullLevo

bullMoxi

bull(Gati)

Oral bacteriostatic 2nd line

Unclear efficacy bullETAPTA

bullPASA

bullCYS

Not routinely recommended

efficacy unknown eg

amoxacillinclavulanic acid

clarithromycin clofazamine

linezolid inmipenemcilastatin

high dose isonizid

XDR= HR + 1 FQ + 1 Injectable (KM or AMK or CM)

Page 19: Updates in TB

Cultures

- Lowenstein Jensen media 6-8

weeks

-Bactec media 2-8days Radiolabelled 14c

labelled palmitic acid

-Mycobacterial growth indicator tube Middbrook broth+o2 sensitive fluroscent sensor to

indicate growthamp bacilli can be identified by Gen

Probe method at the same day of detection

Diagnosis of Active TB

Acid fast stain of sputum

Sputum AFB culture (culture needed for drug susceptibility)

Radiographic imaging (CXR CT)

PCRNAT

Fluid Aspiration

Tissue biopsy ndash higher yield than fluid

Direct Methods 1-Direct Microscopy (ZN Kinyoun Flurochrome) 2-Culture (Traditional Rapid methods) 3- Detection of DNA or RNA of mycobacterial origin ( PCR LAMP TAA NAA LCR Fast Plaque)

Direct Microscopic

Examination Hallmark of staining is Ziehl-Neelsen stained

slides

Easiest amp quickest diagnostic test

Limited sensitivity (46-78) but specificity is

virtually 100

Centrifugation amp flurochrome staining

(auramine O) with UV microscopy markedly

increase the sensitivity amp a large number can

be examined in a much shorter time Chest 1969951193

Direct Microscopic

Examination 1048708 ZN staining requires = 105

bacilliml

1048708 TB bacilli appear as straightcurved rods (1-4μ x

02-08μ) singly in pairs or in

clumps

1048708 The yield of microscopic

examination correlates well with the extent of disease the

presence of cavitation and the

quality of specimen

1048708 It is a good marker for

infectiousness amp the response to the treatment

Several approaches are being made to

enhance the

sensitivity of the smear microscopy

1048708 Concentration of sputum sample by centrifugation

enhances sensitivity to almost 100

1048708 Treatment of sputum samples with Zwitterionic

detergent also known as C18

carboxyprophylbetaine(

CB18) interferes with the innate

buoyancy of the bacilli and enhances the result of

sputum microscopy J Clin Microbiol 199931 2371

J Clin Microbiol 199836 1965

Traditional Culture 1048708 More sensitive amp can be positive even when

bacterial load is low

(10-100 bacilliml)

1048708 Sensitivity 80-85 Specificity 98 1048708 Required for precise identification of causative

organisms

1048708 3 Types of media are used

1048708 Egg based LJ Petragnani and ATS

1048708 Agar based Middlebrook 7H10 or 7H11 1048708 Liquid based Kirschnerrsquos Middlebrook 7H9

1048708 Growth is slow and takes 6-8 weeks There after

the same length of

time is required for complete identification amp sensitivity

testing

Broth Based Rapid Culture

Methods 1048708 Micro colony detection on solid media

1048708 Radiometric (BACTEC)

1048708 Septicheck AFB

1048708 Mycobacterial growth indicator tubes (MGIT)

1048708 Substantial improvement in time to detection amp total number of positive cultures can be realized from using broth based systems

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

Micro colony Detection on Solid

Media 1048708 Plates poured with thin layer of

Middlebrook 7H11

agar medium are incubated and examined

microscopically on alternate days for the first 2 days

and less frequently thereafter

1048708 In less than 7 days micro-colonies of

slow growing

mycobacteria such as Mtb can be detected

BACTEC 1048708 Growth is ascertained

by liberation of 14CO2

as metabolized by

mycobacteria amp

detected by BACTEC

460 instrument amp

reported in terms of growth index (GI) value

BACTEC 1048708 Average time to recovery of Mtb from

smear positive specimens is 8 days

1048708 When smear negative culture positive

samples are

examined mean time for detection is 14

days 1048708 More sensitive than traditional

method

1048708 Can also be used for drug

susceptibility testing J Clin Microbiol 199432 918-925

BACTEC 1048708 A special procedure unique to

BACTEC system for identification of Mtb complex is based on

observation

that p-nitro-α-acetylamino-β-

hydroxypropiophenone

(NAP) will inhibit organisms belonging to Mtb complex

while having little or no effects on other

mycobacteria

1048708 Drawbacks

1048708 Cost 1048708 Problem of disposal of radioactive

waste

Septicheck AFB 1048708 Combines broth amp solid media into a

single device (biphasic culture approach)

1048708 Contains 30ml of modified Middlebrook

7H9 broth in CO2

enriched culture bottle amp a peddle with

agar media- one side of peddle covered with Middlebrook

7H11 other

side contains Middle brook 7H11 with NAP

1048708 Requires 3 weeks of incubation

1048708 Advantage Simultaneous detection of Mtb NTM other

respiratory pathogen amp even contaminant

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Rapid Method

1048708 Consists of round bottom tubes

containing 4 ml of

modified Middlebrook 7H9 broth which has an oxygen

sensitive fluroscent sensor at the bottom

1048708 When mycobacteria grow they deplete

the dissolved

oxygen in the broth amp allow the indicator to fluoresce

brightly in a 365nm UV light J Clin Microbiol 199937 748-752

Mycobacterial Growth Indicator

Tube (MGIT) 1048708 Positive signals are obtained in 10-12

days

1048708 MGIT can also be used as a rapid

method for the detection of drug resistant strains of Mtb

directly from

acid-fast smear positive samples as well as

from indirect

drug susceptibility studies 1048708 Advantages over BACTEC

1048708 Cheaper

1048708 No problem of radioactive waste

disposal J Clin Microbiol 199937 45-48

Detection and identification of mycobacteria

directly

from clinical samples 1048708 Genotypic Methods

1048708 PCR

1048708 LAMP

1048708 TMA NAA

1048708 Ligase chain reaction

1048708 Phenotypic Methods

1048708 FAST Plaque TB

Polymerase Chain Reaction

(PCR) 1048708 Essentially PCR is a way to make

millions of identical

copies of a specific DNA sequence which

may be a gene or a part of a gene or simply a

stretch of

nucleotides with a known DNA sequence

the

function of which may be unknown 1048708 A specimen that may contain the DNA

sequence of

interest is heated to denature double

stranded DNA

Polymerase Chain Reaction

(PCR) 1048708 Specific synthetic oligonucleotide

primers bind to the

unique DNA sequences of interest and a

heat stable DNA polymerase (Thermus aquaticus)

extends the

primer to create a complete amp

complimentary strand

of DNA 1048708 This process is repeated sequentially

25-40 times

thereby creating millions of copies of target

sequence

Polymerase Chain Reaction (PCR) 1048708 65 Kd antigen (HSPs)

1048708 Used earlier

1048708 Heat shock protein believed to be

distinct from other bacterial HSPs

1048708 This gene is identical in all species of

mycobacteria

1048708 Therefore unsuitable for detecting Mtb

particularly in areas where species like Mavium

or Mkansasii are prevalent

IS6110

1048708 It is a transposon which are

self replicating stretches of

DNA

1048708 Function not known 1048708 This sequence has been found in the

Mtb complex

organisms (Mtb Mafricanum Mmicroti

Mbovis)

1048708 IS6110 sequence generally occurs only once in Mbovis

but is found as often as 20 times in certain

strains of Mtb

thus offering multiple targets for

amplification

Polymerase Chain Reaction

(PCR) 1048708 With recent modification PCR can

detect even a fraction

of a bacilli

1048708 Role in pulmonary TB 1048708 Detects nearly all smear +ve and

culture +ve cases

1048708 Useful technology for rapid diagnosis of

smear ndashve cases

of active TB 1048708 Able to identify 50-60 of smear -ve

cases this would

reduce the need for more invasive

approaches to smear -

ve cases

Distinguish Mtb from NTM in smear +ve

cases as

IS6110 sequence is not found in NTM

1048708 Should not be used to replace sputum

microscopy 1048708 Sensitivity specificity amp PPV for PCR is

835

99 amp 942 respectively Am Rev Respir Dis 1991 1441160 J Clin Microbiol 199931 2049-2055

Polymerase Chain Reaction (PCR) 1048708 Role in Extrapulmonary TB

1048708 Limited Role

1048708 No comprehensive large series

comparing the yield of PCR with other available

approaches has

been published

1048708 But at present it is valuable adjunct in

the diagnosis of TBM pleurisy pericardial TB

amp other

condition in which yield of other tests are

low

Polymerase Chain Reaction (PCR) 1048708 Disadvantages

1048708 Very high degree of quality control

required

1048708 Variation from lab to lab remain significant

1048708 In pts on ATT PCR should not be used

as an

indicator of infectivity as this assay remains

+ve for a greater time than do cultures Am J Respir Crit Care Med 1997155 1804-1854

High false +ve results in patients previously

treated with ATT in contacts of sputum +ve

active

cases

1048708 High Cost 1048708 So better understanding of how to use

these

tests in conjunction with available clinical

information is essential Thorax 199247690-694

LAMP 1048708 Loop-mediated isothermal

amplification 1048708 It is a novel nucleic acid amplification

method in which

reagents react under isothermal conditions

with high

specificity efficiency and rapidity 1048708 LAMP is used for detection of Mtb complex Mavium

and Mintracellulare directly from sputum

specimens as

well as for detection of culture isolates grown in a liquid

medium (MGIT) or on a solid medium

(Ogawarsquos

medium)

Iwamoto T et al J Clin Microbiol 200341 2616-2619

LAMP 1048708 This method employs a DNA

polymerase and a set of four specially designed primers that

recognize a total of

six distinct sequences on the target DNA

1048708 Species-specific primers were

designed by targeting the gyrB gene

1048708 Simple procedure starting with the

mixing of all reagents

in a single tube followed by an isothermal

reaction during which the reaction mixture is held at

63degC

1048708 60-min incubation time

LAMP 1048708 Due to its easy operation without

sophisticated equipment it will be simple enough to use

in

1048708 Small-scale hospitals

1048708 Primary care facilities

1048708 Clinical laboratories in developing

countries

1048708 Difficulties 1048708 Sample preparation

1048708 Nucleic acid extraction

1048708 Cross-contamination

TMA NAA 1048708 Transcription Mediated Amplification

(TMA) 1048708 Nucleic Acid Amplification (NAA)

1048708 These techniques use chemical rather

than biological

amplification to produce nucleic acid

1048708 Test results within few hours 1048708 Currently used only for respiratory

specimens

Ligase Chain Reaction 1048708 It is a variant of PCR in which a pair of

oligonucleotides are made to bind to one of the DNA

target strands so that they are adjacent to

each

other

1048708 A second pair of oligonucleotides is designed to

hybridize to the same regions on the

complementary

DNA

Ligase Chain Reaction 1048708 The action of DNA polymerase and

ligase in the presence of nucleotides results in the gap

between

adjacent primers being filled with

appropriate

nucleotides and ligation of primers 1048708 It is mainly being used for respiratory

samples and

has a high overall specificity and sensitivity

for smear

+ve and ndashve specimens

FAST Plaque TB 1048708 It is an original phage based test

1048708 It uses the mycobacteriophage to detect the presence of

Mtb directly from sputum specimens

1048708 It is a rapid manual test easy to

perform and has a

higher sensitivity than microscopy in newly diagnosed

smear +ve pts

Int J Tuberc Lung Dis 19982 160

Indirect Methods 1048708 Antibody detection

1048708 TB STAT-PAK

1048708 ELISA

1048708 India test TB 1048708 Antigen detection

1048708 TB MPB 64 patch test

1048708 Quantiferon-GOLD test

1048708 Biochemical Assays (ADA Bromide

Partition Gas

Chromatography)

TB STAT-PAK 1048708 Immuno-chromatographic test

1048708 Has been evolved with a capability to differentiate

between active or dormant TB infection in

whole blood

plasma or serum

1048708 Its value in in disease endemic countries is yet to be

ascertained Eur Resp J 19958 676

Antibody detection by ELISA 1048708 Several serodiagnostic tests

principally those using ELISA methodology for measurement of

IgG Ab are

available

1048708 38-Kd Ag provides serodiagnostic test

with most favorable test characteristics described

but is limited by

the lack of purified Ag

1048708 Serum IgG Ab are observed to rise

during the first 3 months of therapy but fall after 12-16

months

Antibody detection by ELISA 1048708 Other purified antigens to which

antibodies are detected

1048708 30 Kd protein antigen

1048708 16 Kd heat-shock antigen

1048708 Lipoarabinomannan(LAM) ndash LAM is a

complex glycolipid associated with cell wall of

mycobacteria amp

is produced in

substantial quantities by growing

Mtb 1048708 A60 antigen

1048708 ES3141 antigen

Antibody detection by ELISA 1048708 IgM Ab levels have usually been found

to be so low that their reliable measurement has been

difficult

1048708 Serodiagnosis with crude Ag gives high

false positive

results 1048708 These tests lack specificity because

polyclonal Ab are

used

1048708 Use of monoclonal antibodies have

increased their specificity

Antibody detection by ELISA 1048708 It takes several months after diagnosis

for patients with pulmonary TB to reach maximum antibody

titers so that

serodiagnosis appears to be more useful in

chronic

extrapulmonary disease (bone or joint) than in acute

forms (miliary TBM)

1048708 Serodiagnosis also has limited utility in

smear negative

patients with minimal PTB In pediatric TB amp in disease

endemic countries with high infection rates

Antibody detection by ELISA 1048708 ELISA also has limited diagnostic

potential in AIDS prevalent population

1048708 Tests are expensive require trained

personnel amp

difficulty in distinguishing Mtb amp NTM

1048708 Serologic tests have not yet demonstrated sufficient

performance to warrant routine use in

control programs Int J Tuberc Lung Dis 20004132 5152-5388

Antibody detection by ELISA 1048708 Sensitivity and specificity of ELISA

serodiagnostic tests using measurement of serum IgG Ab to

selected

mycobacterial Ag

Antigen Sensitivity Specificity

38 Kd 49-89 98-100 30 Kd 62-72 97-100

16 Kd 24-71 97-99

LAM 26-81 92-100

A60 71-100 71-95