Mycobacterium Flashcards by Mandeep Chandi

What bacteria are apart of Mycobacterium?

Tuberculosis

- Leprae

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What kind of stain do you use for mycobacterium species?

Acid fast stain

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It takes very long to develop a mycobacterium disease because why?

because the generation time (doubling time) is about 20 hours.

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What bacteria are apart of the M. avium complex (MAC complex)

M. avium subspecies avium
M. avium subspecies silvaticum
M. avium subspecies paratuberculosis

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M. avium complex (MAC) causes what sort of complications?

Opportunistic infections in AIDS

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What bacteria are apart of the M. Tuberculosis complex?

M. tuberculosis
M. africanum
M. bovis
M. microti
M. caprae

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Which mycobacterium causes buruli ulcer?

M. ulcerans

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Which mycobacterium causes swimmers ulcer or fishtank granulomas?

M. Marinum

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what is the cell wall of M. tuberculosis made of?

mycolic acid

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Characteristic of M. tuberculosis?

obligate aerobic bacilli
Acid fast bacteria
very fastidious (only grows when specific nutrients are present)
Very slow (~20hr doubling)
resistant to common antibiotics

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What are the 4 obligate Aerobes?

“Nagging Pests Must Breath”

Nocardia
Pseudomonas
Mycobacterium
Bacillus

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What stain do you use for M. tuberculosis?

Ziehl-Neelsen Stain

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How do M. tuberculosis appear when stained with Ziehl-Neelsen Stain?

Bright red bacilli (rods)

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What sort of colonies of M. tuberculosis are formed on Lowenstein Jensen medium?

Rough, Buff, and Tough colonies

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What kind of media do you use for M. tuberculosis?

Lowenstein-Jenson Media (Midlebrook medium)

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1 of 4 deaths in M. tuberculosis is related to what?

HIV-related

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What is the route of transmission for M. tuberculosis?

Person to person transmission by infectious aerosols

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These kind of people are more prone to have M. tuberculosis…?

Medically underserved
Poor
Homeless
Prison inmates
Alcoholics

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What are the VF of M. tuberculosis?

LAM
Cord factor glycoprotein
Mycolic acid

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What is the role of Lipoarabinomannan (LAM)?

Inhibits macrophage activation

- Prevents phagosome fusion with lysosome

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What is the role of Mycolic acid?

Makes M. tb resistant to complement

- IMPORTANT in granuloma formation

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What is the role of Cord factor?

Interferes with phagosome maturation

- Induces release of TNF-alpha

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What is the role of 19kDa Lipoprotein?

Induces apoptosis in late stage of infection

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What is the role of PDIM (pthiocerol dimycocerasate)?

Interferes with MHC-II loading in vacuole

- May prevent pH from lowering

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Pathogenesis of primary infection with M. Tb

- organism engulfed by Alveolar macs - non resistant macrophages attracted - macrophages transport bacteria to hilar LN - CMI stimulated

What is involved in Ghon complex?

Lung lesion + Enlarged LNs

In M. Tb, the CMI leads to formation of what?

Tubercles/Granulomas

Progression of M. Tb leads to what?

cavitation or bursting of contaminated MTB

Large granuloma histological findings?

- Necrotic center - caseous with fibrin, liquid, calcification - Breaks open to release bacteria

where to MTBs reside?

in macrophages

Clinical findings of a chronic disease?

- Calcification - Fibrosis, scarring - persist for life - Show up as radio-opaque nodules

Reactivation of dormant M. Tb is usually where?

Apex of the Lung

Tubercles are found in many tissues including?

- Bones: Potts disease - Kidney: Cement or Putty kidney - Meningitis - Liver - Gut

Miliary TB is also called?

Disseminated TB

Disseminated TB is characterized by what?

- wide spread into the human body via blood stream in the macrophages. - They resemble millet seeds

What is the diagnosis steps for M. Tb?

1. Tuberculin Skin test (positive) 2. Chest x-ray and clinical exam (abnormal) 3. Sputum culture (positive) 4. Active TB treatment

how many consecutive sputum samples do you have to take in order to consider positive MTB?

3 consecutive sputum cultures. (treat with 2% NaOH)

If chest x-rays are normal for MTB and sputum culture is negative for MTB what does this mean?

Latent Tuberculosis

What kind of hypersensitivity type is the Mantoux Tuberculin test?

Type IV, CMI response

Mantoux test in Exposed/HIV+ individual?

5-9mm positive if person is in category 1

Mantoux test in High risk/HIV- individual?

10-14 mm positive if person in category 2

Mantoux test in Low Risk/HIV- individual?

Greater then or equal to 15mm positive if person in category 3

M. Tb x-ray shows what?

Cavity like lesion in upper lobe of lung

what are the sputum culture biochemical tests for M. TB for Niacin, Nitrate reductase and Catalase?

- Niacin is (+) - Nitrate reductase is (-) - Catalse is (-)

What are the pros and cons for using Sputum Immunofluorescence for diagnosing M. Tb?

pros: don't have to wait for culture | - too few bacilli in sample

What stain do you use for M. TB sputum immunofluorescence?

Rhodamine-Auramine Stain - high sensitivity - low specificity

What is the Quantiferon TB test?

Patients blood sample is mixed with Tb antigens in vitro.

What does the Quantiferon diagnostic TB test quantitate?

it quantitates INF-Y production by pre-sensitized cells.

What is the treatment for M. TB for 2 months?

- Isoniazid - Rifampin - Pyrazinamide - Ethambutol

What is the treatment for M. TB for 4-6 months?

- Isoniazid | - Rifampin

What do you use as treatment of M. TB if bacteria is Multi-drug resistant (MDR)?

- Pyrazinamide | - Ethambutol

What do you use as treatment of M. TB if bacteria is Extensively drug resistant (XDR)?

Fluoroquinolones (Ciprofloxacin)

what is the Bacillus calmette Guerin (BCG) vaccine prepared from?

Live attenuated M. bovis strain

What are the symptoms of Mycobacterium tuberculosis infection?

- Bad cough lasting 3 weeks or longer - Cough up blood - weakness - weight loss

M. Leprae is similar to M. TB, except for the following?

- Cannot grow in cell free culture - Prefer lower temps - Affects human and animals (armadillos) - Targets nerves of the extremities

M. Leprae's 2 disease manifestations are due to what?

due to Th1 or Th2 response

what are "leonine facies" of Lepromatous leprosy?

- Loss of eye brows - Nasal collapse - Lumpy earlobe

What is the reservoir for Mycobacterium Leprae in USA?

Armadillos

Leprosy is also known as?

Hansen's Disease

What are Hansen's disease 2 forms?

- Lepromatous | - Tuberculoid

What is Lepromatous leprosy characterized by?

Low cell mediated immunity with a humoral Th2 response

What is Tuberculoid leprosy characterized by?

High cell mediated mediated immunity with a largely Th1 type immune response

Which Mycobacterium complex has a very strong associated with AIDS patients?

M. avium complex (MAC)