Doctor Hamid Al Zoubi

Waseem Abu Obeida

Corrected by

Done by ةّ يمجع وبأ مها

number 15

In case you don’t know

- (Bacillus = rod) and (bacilli = rods)

- hypersensitivity tests can be either immediate (within few hours or less)

or delayed, in this sheet, we are discussing the delayed test.

- Dormant (from the verb dormir which means sleep)

- Focus = many foci & bacterium = many bacteria

Mycobacteria:

• Mycobacteria tuberculosis.

• Mycobacteria leprae.

❖ Mycobacteria tuberculosis

• Mycobacterium tuberculosis (M. tuberculosis) – is a strict aerobic bacillus.

• It affects 50% of people worldwide (about 2 billions).

• It causes death to 3 million (Tuberculosis (TB) increases, when immunity

responses are lowered as a result of chemotherapy and HIV infections).

• MDR (multi-drug resistant tuberculosis) is one of the problems, we are

facing today.

The ‘M. tuberculosis complex’ are human pathogens that cause tuberculosis,

the complex includes:

1. M. tuberculosis

2. M. africanum

3. M. bovis

4. M. canettii

Notes:

• M. canetti has smooth colonies but M. tuberculosis has rough colonies.

• The mycobacteria are characterized by thick lipid-rich cell walls (thick

mycolic acid), this is why they are stained by ‘acid-fast’ / ‘ziehl neelson’

stains, so we don’t use gram stains because of their hydrophobicity.

mycobacteria are characterized by ‘acid-fast’ staining property. Most of

them are strict aerobic acid-fast bacilli.

• They are killed by UV, Alcohol, many types of aldehydes, they are also

destroyed by pasteurization (heat sensitive).

• They are resistant to alkalis, acids and ammonia.

• Growth Media

-Löwenstein–Jensen (LJ) medium is an egg–glycerol-based medium to which

malachite green dye is added to inhibit the growth of other bacteria (other

than mycobacteria) and to provide a contrasting colour against which

colonies of mycobacteria are easily seen. (something like a background)

-Liquid medium, enriched with bovine serum albumin.

Note: Liquid medium is more rapid (takes about 10 days) but Löwenstein–

Jensen (LJ) is slow, it takes more time (6-8 weeks), because the bacterium

that causes TB is slow growing.

• Pathogenesis: (commonly in lungs)

( immune response by CD4 T helper cells)

If a malnourished patient from a poor environment, with fever (rise in his body

temperature), weight loss, sweating, think about TB as a possibility.

TB vaccines (BCG) are given intradermally (age: 1st month), some countries don’t

provide TB injections, why? Because TB tests cannot distinguish active disease

from past vaccination, meaning If a person was immunized against TB, the result

would be a positive test, because antibodies were produced by vaccines – but if

the person is not already vaccinated, one option is left, he is latently infected/

have the disease- (bear with me, this will be discussed in more detail in the

following pages).

What Slides Say:

o Lung Primary TB:

Macrophages 1 in alveoli > Ghon’s focus > To hilar lymph nodes > primary TB

complex > PTB attacked by Macrophages 2 (O2 consumption) > surrounding the

lesion in granuloma (caseation) > latent Tuberculosis (TB) TB in other places:

Skin, intestine and lymph nodes

o Post Primary TB

90% of primary infections > latent > reactivation or reinfection > post primary

TB

Reactivation of primary TB > Post primary TB (Also due to REinfection): • Same

as in primary but tuberculoma instead of granuloma • Spread to LLL, upper

airways, bladder, skin (Lopus vulgaris) and bladder (more spread and infectivity)

o Secondary and Milliary TB

10% of primary > secondary TB > meningitis, pott’s disease, urogenital and skin

involvement (s.t milliary TB if opened into a blood vessel > disseminated)

crossword puzzle? Let’s try to solve it.

Note: we wrote what the doctor said, you might find some differences when referring to

greenwood or any other source.

Initial infection is commonly in the lung, (inhalation of mycobacteria). The

alveolar macrophages (Macrophages1) engulf the inhaled bacteria in the alveoli

(leading to the formation of Ghon’s focus,), Some bacteria are carried to the

hilar lymph nodes, then the primary TB complex is formed, then this PTB

complex is attacked by another type of macrophages (macrophages 2 :/), these

macrophages consumes oxygen decreasing the amounts of O2 reaching the

bacteria thus killing it, PTB complex plus macrophages 2 form granuloma and

caseation necrosis.

(In addition to lungs, Tuberculosis can occur in other places such as skin,

intestine and lymph nodes)

Then in 90% of patients (with good immune responses), primary infections

become latent (dormant foci), then when immunity becomes low for one reason

or another, Reactivation of dormant foci of tubercle bacilli or exogenous

reinfection leads to post-primary tuberculosis, this leads to post primary TB

(reactivated latent), The same process of granuloma formation occurs, but the

caseation areas here are called tuberculoma, forming cavities in the lungs and

spread to the bronchi ,so it will be very infectious and transmitted by coughing,

it can also spread to LLL (lower lung loop), upper airways, bladder, skin (Lupus

vulgaris) and bladder (more spread and infectivity).

What about the remaining 10%? (those who are immunocompromised)

Secondary TB arises from the primary TB directly which gives rise to the serious

manifestations including meningitis, pott’s disease (spine), urogenital and skin

involvement. If a focus of infection ruptures into a blood vessel, bacteria are

disseminated throughout the body, This, is known as miliary tuberculosis. (it is

when bacteria reach the bloodstream , dissemination throughout the body)

- Immunocompromised (10%): primary TB> secondry TB>miliary TB (in some

cases).

- Immunocompetent (90%): primary TB (granuloma)>latent TB>post-primary

TB (tuberculoma).

Extra note:

Infection is different from disease. Infection is producing a focus of organisms

(e.g.: bacteria) which may or may not cause tissue damage (i.e, disease), as we

said before, when the bacteria (mycobacteria/ tubercle bacilli) remain dormant,

the person is infected but does not have the active disease and therefore cannot

transmit bacteria to others. In other words, if there was no reactivation of these

bacteria or reinfection, the mycobacteria stop at the latent stage and the person

will not develop post-primary TB) it is as if these bacteria are kept sleeping.

If this person was lucky enough, the bacteria might remain dormant forever.

(special thanks to Kumar, Abbas and Aster)

Clinically:

The following factors increase the likelihood that a patient will have

tuberculosis (TB):

o HIV infection

o History of prior TB treatment (especially if there was no

compliance).

o TB exposure, Travel to or emigration from a TB endemic area.

o Homelessness, shelter-dwelling, incarceration (malnutrition).

Symptoms

Classic features associated with active TB are as follows:

Cough

Weight loss/anorexia

Fever

Night sweats

Hemoptysis (coughing up of blood)

Chest pain

Diagnosis:

Diagnosis of post- primary found in upper lung loop :/

(According to Greenwood: For unknown reasons, reactivation or reinfection

tuberculosis tends to develop in the upper lobes of the lungs)

- Labrotary diagnosis:

o Stain: Acid fast stain (Ziehl–Neelsen stain)

o Culture

• 6-8 Weeks on LJ

• less time in liquid medium

o Interferon Gamma interferon

o PCR (polymerase chain reaction)

- History and examination:

o Chest x-ray (CXR).

o PDD (purified protein derivative) also known as, Mantoux test/

tuberculin test.

2-12 Weeks post infection, an antigenic part of the mycobacteria is

injected intradermally, a delayed hypersensitivity in skin occurs 2-3 days

after exposure to the antigen whether it is an active infection (that will

cause Tuberculosis), vaccine (BCG), environmental mycobacteria (from

environment, non-tuberculous mycobacteria).

IGRT? interferon gamma release test is promising, though not without

problems of specificity, it detects interferon-γ-producing peripheral blood

T cells that respond to antigens present only in the bacteria of the active

infection. (not environmental or BCG)

(to whom it may concern, since we have much time, and we have nothing to do

except Micro, The doctor said:” read more about IGRT”, well, if we found a

question in our exam about it, our reference in this course would be anything

on Earth but not Greenwood(

Back to the PDD test:

according to the tuberculin skin test reaction,

if the diameter was 5 in immunocompromised people, the result would

be a positive test.

If the diameter was 15, the result would be positive in any person.

Note: As i previously said, tuberculin test is a skin test, meaning that hypersensitivity reaction occurs and appears on your skin , if the induration was 5 millimeter or more in the first group like those who are HIV infected and other immunocompromised patients, this would indicate that they have mycobacteria (either BCG vaccinated, got it from environment or are TB victims) but if it was less than 5, then this would indicate that it is just a normal hypersensitivity and they don't have this bacteria ... but in any person, whether immunocompetent or immunocompromised, if the induration was more than 15, this would indicate the presence of bacteria too from the vaccine, environment, disease and in immunocompetent people, if induration was less than 15, this would indicate that the bacteria might be absent

(The only thing, the doctor said about this table(

Management:

Isolation: (isolating a patient in a room to prevent him from transmitting

the disease to others outside the room).

Combination of medicines,

DOTS

(DOTS: Directly Observed Treatment Short-course, a strategy to reduce TB

cases, in DOTS healthcare workers observe patients as they take their anti-

TB medicines, compliance is really important)

Treatment:

(1st line anti TB)

4 drugs are used for 6 months

(first 2 months of REFINA ((rifampicin & isoniazid) +Ethambutol and

Pyrazinamide) (the following 4 months, we use only REFINA ((rifampicin

& isoniazid)))

(2nd line treatment in MDR (multi-drug resistance):

Macrolides, Fluroquinilones, aminoglycosides, cycloserine...

(3rd line treatment)

Linezolid, rifabutin, arginine, vitamin D..

Note: if there was resistance to the first line, second line treatment is used

Prevention:

• by BCG *Bacille Calmette–Guérin* it is a life attenuated vaccine,

it doesn’t kill mycobacteria, it keeps them viable (alive)

• BCG vaccine has a documented protective effect against

meningitis and disseminated TB in children. – remember:

children’s immunity is weak-

❖ Mycobacterium leprae

• stained by Acid fast

• aerobic

• Intracellular bacilli

• similar to M. Tuberculosis (Leprosy bacilli resemble tubercle bacilli in their

general morphology)

• fat in cell wall, M. leprae has a characteristic surface lipid that can be

extracted from it.

• It causes leprosy (Hansen’s disease)

chronic granulomatous disease principally affecting the skin, mucous

membrane, peripheral nervous system and anterior chamber of eyes. The

infection often causes severe disfigurement and deformity, it might lead to

loss of sensation since peripheral nervous system is affected.

• Approximately 2 million cases worldwide; Africa, Asia and south America

(India, Nepal, Tanzania, Brazil, Madagascar, Mozambique)

MOT (mode of transmission):

• Inhalation (respiratory droplets)

Incubation period on average is 4-8 years (1-30 years)

Pathogenesis: (determined by the immune response)

• Brief bacteremic phase

• Binds to macrophages and Schwann cells

• immune response

Clinically:

• Thickened lesions of skin / nodules

• Nerve thickening and Loss of sensation (muscle weakness, tissue /organ

and nasal septum destruction, ulcers...)

• Disfigurement and mutilation

Classification (types of leprosy)

1) Tuberculoid (Paucibacillary) leprosy

o There are Few skin lesions ( less than 5 lesions)

o Usually no acid fast bacilli seen in the lesions

2) Lepromatous (Multibacillary) leprosy

o skin lesions ( more than 5)

o Many acid fast bacilli seen in lesions

o More in cold areas (nose, ear, knees, elbow and buttocks)

o ‘Leonine facies’ = (a lion-like face)

3) Borderline leprosy

Note : it is important to know whether it is a multibacillary or paucibacillary, for

the selection of treatment.

Diagnosis

Specimens: Full thickness skin biopsy, skin scrapings and nasal smears (trivial

extra: tuberculosis specimen is certainly sputum)

- Acid fast staining and histological examination:

Not only for diagnosis but Also for diseases classification and therapy

monitoring

- Molecular techniques (probing and PCR which is Promising

- Culture:

• not available in vitro (intracellular)

• Grown in mice footpads, athymic mice and in Armadillo

Armadillo This animal has therefore provided sufficient

bacilli

Treatment:

- Effective treatment is available:

1) Paucibacillary Dapsone + Rifampicin • 6 months

2) Multibcillary Dapsone+Rifampicin+Clofazamine • 12 months

Sorry for any mistake, writing micro sheets ain’t that easy, I was being so

sweet while writing this sweet sheet of the sweetest course of this semester,

which is being taught by the super-sweet doctor 💚