Microbiology PHT 123

2010-20112nd Term 2nd Semester

Haemophilus Spp (Blood-loving bacteria)H. Influenzae

Does not cause influenza, Why named so? mistakenly considered the cause of influenza 1890 Pandemic.

Gram negative coccobacilliObligate parasites of manCause hidden disease because:

Does not cause a specific disease Responding first with antibiotics may mask Hib's Difficult to isolate

Fastidious, require X (hemine) and V (NAD or NADP) factors in chocolate agar

A "Rapid Assessment Tool" has been developed by WHO and CDC to make sensible estimates of Hib

H. Ducreyi : STD (soft chancroid) not commonOpportunistic Haemophilus pathogens are rare

H. Influenza have no specific syndrome but

can cause:meningitis, conjunctivitis, sinusitis, cellulitis, otitis, epiglottitis, pneumonia,

Health Canada and www.cdc.gov/vaccines/pubs

One of the most transformable genomes

H. Influenza was the first free living organism to have the complete genome sequenced in 1995

The genome consists of 1.8 MB of DNA in a single circular chromosome of which 1.7 code for proteins.

How does it become highly-specific to humans?. Mutations,Transformable by many ways, Phase variation by DNA repeats

Diagnosis

Microscopy to detect in CSF, synovial fluids, Culturing, difficult, may be not sensitivelatex particle agglutination test (LAT)PCR

H.Influenza Gram stain H.Influenza Choclate agar

Treatment and prophylaxis cefotaxime , ceftriaxone, ampicillin and

sulbactam, cephalosporins of the second and third generation, or fluoroquinolones are preferred.

Hib conjugate vaccineHib is preventable, but there are two

problems:A shortage of information : difficult to diagnose,

it causes death without being recognizedExpensive: Hib vaccine is expensive

VibrioV. cholerae, and V. parahaemolyticus are human pathogens

V. cholerae: cause cholera. Comma shaped rods , with Two circular chromosomesWhat is Cholera? Cholera toxin activates adenyl cyclase causing

increased cAMP level and hypersecretion of fluids and electrolytes

Extensive watery diarrhea (15-20 liters/day) called Rice-Water Stool:· Colorless· Odorless· No protein· Speckled with mucus

Source contaminated waters and foodCaused 8 cholera pandemics, example of Pandemic strain is

El TorTreatment and prevention

· Rehydration & supportive therapy· Water purification, sanitation & sewage treatment· Vaccines

Sack, David, et al. 2004. Seminar: Cholera. The Lancet. 363: 223-233.

DiagnosisRapid tests

Dark-field microscopyRapid immunoassaysMolecular methods – PCR & DNA probes

Selective/differential culture medium - Thiosulfate Citrate Bile salts Sucrose (TCBS) agarV. cholerae grow as yellow colonies

Biochemical and serological tests

HelicobacterH. pylori = gastritis, peptic ulcer disease(PUD)

Helical (spiral or curved) corkscrew shape and lophotrichous (tuft at one pole)flagella helps in penetration and colonization of mucosal lining of stomach & duodenum

Acid-inhibitory proteinHydrolyzes urea and inhibits acids in gastrics

• Most gastric cancers are preceded by an infection with H. pylori

Microaerophilic: Change chape to coccoid when exposed to oxygen or upon prolonged culture

Diagnostic aspectsDetected in endoscopic antral gastric biopsy materialCulture media containing whole or lysed bloodMicroaerophilic does not ferment or oxidize carbohydrates

Triple Chemotherapy (synergism):Proton pump inhibitor (e.g., omeprazole =

Prilosec(R))One or more antibiotics (e.g., clarithromycin;

amoxicillin; metronidazole)Bismuth compound

Mycobacterium tuberclosis: Tuberclosis 1/3RD of World has it, a global Emergency.

TB what it is, and how it spreads? Outside body Inside body:

Spreads through the air when a person with TB:

Coughs

Speaks

Laughs

Sneezes

Sings

bacilli go to lungs and infect alveoli

Macrophages attack bacteria, but some survive

Infected macrophages form tubercles

Dead cells form granulomas

http://www.cpmc.columbia.edu/resources/tbcpp/abouttb.html.

Symptoms for Pulmonary TB:There are many types of Tuberclosis, pulmonary

is most important

Perpetual Cough

Fever

Weight loss

Night sweats

Loss of appetite

Fatigue

Swollen glands

Chills

Pain while breathing

Types of TB bacteria include:

Mycobacterium tuberculosis

Mycobacterium leprae

Mycobacterium avium

Some diagnosticsAcid fast staining, and Lowenstein-Jensen

AgarSkin test- Mantoux testPurified Protein Derivative PPD injected in

forearm and examined 2-3 days laterRed welt around injection indicates infectionExamine medical history, x-rays, and sputum

Treatment and preventionTake antibiotics for 6-12 monthsPreventative drug to destroy dormant bacteriaFor active TB, 4 medications: isoniazid,

rifampin, ethambutol, and pyrazinamideVaccines (relatively ineffective today)Check with X-ray

Mycobacterium leprae, Leprosy (uncommon)

Spirochetes: Treponema, Borrelia, & Leptospira

Spirochete means “coiled hair” Greek. They are tightly coiled like telephone cord, only a fraction of a micron in diameter but hundred of microns long

Twisting Motility by periplasmic flagella (axial fibrils or endoflagella) is a major difference between this and other bacteria

Spirochaetes: Genus TreponemaGenus: Treponema: Treponema pallidum, causes

syphilis (sexually, or congenitally transmitted), delicate obligate parasite

Stages of Syphilis:1. Primary Chancre lesion is the main sign

2. Secondary rash

3. Latent , no sign but bacteria present

4.Tertiary, very complicated systemic

Treponema pertenue, causes yawsskin lesion

SpirochetesGenus: Borrelia

Borrelia burgdorferi, Causes a zoonotic vector borne disease called Lyme disease Transmitted by ticks Linear chromosome

Borrelia recurrentis, causes relapsing feverGenus: Leptospira

Leptospira species, causes leptospirosisMain Diagnostic tests for Spirochetes:

Darkfield microscopyFluorescent antibody stainingVDRLWasserman TestHemagglutination tests

Treatment and control

Penicillin remains drug of choice• WHO monitors treatment recommendations• 7-10 days continuously for early stage• At least 21 days continuously beyond the

early stage Prevention of Mother-child transfer by

barrier methods (e.g., condoms) Prophylactic treatment of contacts

identified through epidemiological tracing

Cautiousness, and morals play significant roles

Rickettsial DiseasesTransmitted by Arthropod Vectors

Fastidious, obligate intracellular bacteria that grow only on cells, eggs, and tissue cultures

Transmitted by Arthropod VectorsThey are pleomorphic & coccobacillaryDo not show on Gram stain, but can be seen with

either Gimenez or Giemsa stains

Gimenez stain of tissue culture cellsinfected with Rickettsia rickettsii

Rickettsial Diseases1. Spotted Fever Group

Rocky Mountain spotted fever

– Rickettsia rickettsiiRickettsial pox– Rickettsia akariCanadian typhus– Rickettsia canada

Mediterranean spotted fever

– Rickettsia conoriiSiberian tick typhus– Rickettsia sibericaQueensland tick typhus– Rickettsia australis

2. Typhus Group

Murine typhus– Rickettsia mooseri (typhi)Epidemic typhus– Rickettsia prowazekiiScrub typhus– Rickettsia tsutsugamushi

3. OthersQ Fever– Coxiella burnetii• Ehrlichiosis– Ehrlichia canis– Ehrlichia equi– Ehrlichia chafeensis– Several others now identified

Pathogenesis and Clinical Symptoms

Pathogenesis for all these infections is very similar regardless of species. A vasculitis (inflammation of blood vessel wall) is caused by the invasion and multiplication of the organism in the endothelial and smooth muscle cells of the blood vessels.

Clinical symtomsThrombosis, occlusion, and necrosis of blood vessel wallsThrombocytopenia with hemorrhage

– occurs primarily as a result of platelet consumption as opposed to true (DIC)disseminated intravascular coagulation

Massive capillary leakage, edema, hypotension, and respiratory distress, encephalitis, myocarditis, & nephritis

Four Prototype Diseases

1. Rocky Mountain spotted fever… by Rickettsia rickettsiiFever, heache, rash…

2. Murine typhus…by Rickettsia typhi3. Epidemic typhus …by Rickettsia prowazekii4. Q fever…by Coxiella burnetii

Occurs in veterinarians, ranchers, and animal researchers from infected placenta of sheep, cattle, or goats (no arthropod vector for C. burnetii). Pneumonia is common

Weil-Felix Reaction and the bit of a history

Historical known that Proteus antibodis cross-reactive with several of the rickettsiae. Today, Weil-Felix test is not confirmed for rickettsial infection.

In Poland during World War II, two physicians cleverly used killed Proteus bacteria to vaccinate the men of a small town, to induce a positive Weil-Felix reaction.

The occupying Germans feared typhus epidemic and Due the vaccination reaction, the village was saved of a certain destruction. The men were not forced into the army, and the women and children were not forced into the camps.

Diagnosis and treatmentSpecific & sensitive tests:

Indirect immunofluorescent antibody (IFA)Indirect hemagglutination antibody (IHA)Complement fixation (CF)

TreatmentIn life-threatening rickettsial infections, early antibiotic

intervention is recommended to prevent endothelial damage

Doxycycline, tetracycline, and chloramphenicol are the drugs of choice

Prevention (transmitted by vectors so avoid them)Use of repellents & protective clothing in endemic areasInspection & removal of ticksVaccine for RMSF is available for risk groupsWeekly doxycycline