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MicroPath > Mycobacteria > Flashcards

Mycobacteria Flashcards

1
Q
  1. List three types of mycobacterial complex.
A 
Mycobacterium tuberculosis complex
•	Mycobacterium tuberculosis
•	Mycobacterium bovis
Mycobacterium avium complex
•	Mycobacterium avium
•	Mycobacterium intracellulare
Mycobacterium abscessus complex
•	Mycobacterium abscessus
•	Mycobacterium massiliense
•	Mycobacterium bolletii
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2
Q
  1. Describe the morphology of mycobacteria.
A

Non-motile rod-shaped bacteria
Relatively slow-growing
Cell wall composed of mycolic acids, complex waxes and glycoproteins
Acid-alcohol fast

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3
Q
  1. What is used as a screening test for mycobacterial infections?
A

Auramine stain

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4
Q
  1. How are non-tuberculous mycobacterial infections transmitted?
A

NOT person-to-person
From the environment
May be colonising rather than infecting

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5
Q
  1. List three examples of slow-growing non-tuberculous mycobacteria and the diseases that they cause.
A

Mycobacterium avium intracellulare
• May invade bronchial tree or pre-existing bronchiectasis/cavities
• Disseminated infection in immunocompromised patients
Mycobacterium marinum
• Swimming pool granuloma
Mycobacterium ulcerans
• Skin lesions (e.g. Bairnsdale ulcer, Buruli ulcer)
• Chronic progressive painless ulcer

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6
Q
  1. List three examples of rapid-growing non-tuberculous mycobacteria.
A

Mycobacterium abscessus
Mycobacterium chelonae
Mycobacterium fortuitum

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7
Q
  1. How is Mycobacterium avium intracellulare treated?
A

Clarithromycin/azithromycin
Rifampicin
Ethambutol
+/- streptomycin/amikacin

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8
Q
  1. What are the two types of Mycobacterium leprae infection?
A

Paucibacillary tuberculoid – few skin lesions, robust T cell response
Multibacillary lepromatous – multiple skin lesions, poor T cell response

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9
Q
  1. How many species are part of the Mycobacterium tuberculosis complex?
A

7 (including Mycobacterium tuberculosis, bovis and africanum)

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10
Q
  1. Describe the natural history of primary TB.
A

Usually asymptomatic
Ghon focus (granuloma in the lungs)
Controlled by cell-mediated immunity
Occasionally causes disseminated/military TB

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11
Q
  1. List some risk factors for reactivation of TB.
A

Immunosuppression
Chronic alcohol excess
Malnutrition
Ageing

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12
Q
  1. List some types of extra-pulmonary TB.
A

Lymphadenitis (scrofula) – cervical lymph nodes most commonly
Gastrointestinal – due to swallowing of tubercle
Peritoneal – ascitic or adhesive
Genitourinary
Bone and joint – due to haematogenous spread (e.g. Pott’s disease)
Miliary TB
Tuberculous meningitis

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13
Q
  1. Which investigation may be done in children with suspected TB?
A

Gastric aspirate

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14
Q
  1. What is NAAT and why is it useful?
A

Nucleic acid amplification test
Allows speciation and the detection of drug resistance mutations
Rapid

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15
Q
  1. What is the tuberculin skin test?
A

A sample of tuberculin is injected intradermally and left for 48-72 hours to observe the response

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16
Q
  1. What are the disadvantages of the tuberculin skin test?
A

Cross-reacts with BCG

Cannot distinguish between active and latent TB

17
Q
  1. What is an IGRA assay?
A

Detection of antigen-specific IFN-gamma production
Does NOT cross-react with BCG
However, it cannot distinguish between latent and active TB

18
Q

List some side effects of TB drugs

A 
a.	Rifampicin 
Raised transaminases 
CYP450 induction 
Orange secretions 
b.	Isoniazid
Peripheral neuropathy (give with pyridoxine)
Hepatotoxicity
c.	Pyrazinamide
Hepatotoxicity 
joint swelling
d.	Ethambutol
Visual disturbance
19
Q
  1. What is multi-drug resistant TB?
A

Resistant to rifampicin and isoniazid

20
Q
  1. What is extremely drug resistant TB?
A

Resistant to rifampicin, isoniazid, fluoroquinolones and at least 1 injectable

21
Q
  1. What are the diagnostic challenges of HIV and TB coinfection?
A

Clinical presentation is less likely to be classical
Symptoms may be absent if CD4+ count is low
More likely to have extra-pulmonary manifestations
Tuberculin skin test more likely to give false-negative
Low sensitivity for IGRAs

22
Q
  1. What are the treatment challenges of HIV and TB coinfection?
A

Timing of treatment
Drug interactions
Overlapping toxicities
Duration of treatment

MicroPath (10 decks)

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