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Mycobacteria and Nocardia Flashcards

1
Q
  • acid fast bacilli with unusual complex and lipid rich cell wall
  • obligate aerobe
  • slow growing
A

mycobacteria

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2
Q

tuberculous pathogens?

A

m. tuberculosis and m.bovis (extrapulmonary Tb)

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3
Q

non tuberculous pathogens?

A

m. kansasii in immunocompromised, MAC disseminated in AIDS

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4
Q

risk factors for Tb?

A

exposure to persons wit Tb, HIV infection, immunosuppressive therapy, homelessness, incarceration, alcohol, illicit drug use, diabetes, chronic pulmonary disease

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5
Q

properties of M. tb:

  • _______ growth rate
  • cell walls with high _____ content provides resistance to antibioitcs, dessication, complement, toxic oxygen species
A

slow

lipid

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6
Q

60% of the cell wall of m tuberculosis made up of?

A

mycolic acid/ lipids

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7
Q

transmission of TB:

  • person to person via ________
  • taken up by __________, via ___ and _____
  • survive intracellularly by preventing?
A

small respiratory droplets

alveolar macrophages, LAM adhesin and C3b opsonization

phagosome lysosome fusion

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8
Q

in immunocompromised patients TB spreads to?

A

bone marrow, spleen, kidneys, CNS

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9
Q

pathogenesis of TB:

  • what type of reaction?
  • secretion of ______
  • lysis of phagocytic cells by ______
  • bacterial killing by activated ________
A

type IV delayed hypersensitivity reaction

IFN-gamma and cytokines

cytotoxic T cells

macrophages

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10
Q
  • expressed by virulent strains of TB
  • glycolipid of trehalose and two mycolic acid
  • disrupts mitochondrial membranes
A

cord factor

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11
Q

latent TB infection

-______ formation of aggregates of activated macrophages, ________ that can fuse into multinucleated ________

A

granuloma

epithelioid histiocytes

Langhan’s giant cells

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12
Q

tubercle formation: large granulomas containing bacilli surrounded by T cells and macrophages encapsulated with ________

A

collagen

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13
Q

calcified primary granuloma

A

Ghon focus

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14
Q

low pathogen burden in TB?

A

self limiting infection and immunity

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15
Q

high pathogen burden in TB?

A

necrosis due to cytokine toxicity, activation of complement cascade, ischemia, hydrolytic enzymes

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16
Q

smaller than pea sized granulomas in TB?

A

cleared from bacteria by activated macrophages

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17
Q

larger necrotic or caseous granulomas in TB?

A

encapsulation with collagen/fibrin, survival of bacteria, reactivation in immunocompromised

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18
Q

early symptoms of pulmonary TB?

A

fever, night sweats, weight loss, malaise

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19
Q

later symptoms of pulmonary TB?

A

nonproductive cough, then productive with bloody sputum, chest pain, shortness of breath

20
Q

primary TB?

A
  • disease within 2 years of infection
  • children
  • heals spontaneously
21
Q

secondary TB?

A
  • post primary reactivation TB
  • greater than 2 years post infection
  • endogenous reactivation of latent infection
22
Q
  • pulmonary and extrapulmonary TB
  • seedlings of TB bacilli, more likely with immunosuppression
  • hematogenous spread to lymph nodes, GU, bone joints, meninges, GI tract
A

miliary TB

23
Q

tuberculosis adenitis usually in the neck

24
Q

dx of TB with radiology reveals lesions where?

A

oxygenated parts of lungs

25
tuberculin (mantoux) skin test is a _______ hypersensitivity response, which screens for ____ TB by injecting _________
type IV delayed latent Purified protein derivative
26
in mantoux TB skin test, redness swelling and induration occur after _____ days, and patients are not positive until ______ weeks after infection
2-3 days 3-6 weeks
27
when reading tuberculin test, measure ______ only
induration
28
limitations of PPD tuberculin test?
anergy (Esp with HIV patients), recent TB infection, very young age, prior immunization, cross reactivity to other mycobacteria
29
alternative to tuberculin test for diagnosis of latent TB, measures M. tb antigens, more specific
IGRA: interferon gamma release assay
30
diagnosis of M. tb?
- acid fast stain of sputum - auramine-rhodamine fluorescent staining of mycolic acid - culture: definitive but slow, on lowenstein jensen media - BACTEC: metabolism - qPCR: good, also detects resistance for isoniazid and rifampin
31
first line drugs for TB active disease?
isoniazid (inhibits mycolic acid synthesis), rifampin, streptomycin, pyrazinamide, ethambutol (inhibits arabinoglactan synthesis)
32
candidates for TB prophylaxis?
positive tuberculin skin test + HIV infection, close contacts with infectious TB, chext Xray with previous TB, injection drug use
33
BCG vaccine contains live attenuated ________, most effective in children, but not recommended in US b/c it affects ________
M. bovis surveillance
34
- transmission by aerosols, contact - obligate intracellular pathogen - infects skin, peripheral nerves (Schwann cells), eyes, mucous membrane, testes - reservoir: humans, primates, armadillos
M. leprae
35
tuberculoid leprosy spectrum - nerve damage? - acid fast bacilli? - Th1 CMI? - Th2 humoral immunity?
2-40 yr incubation, neuropathies and enlarged peripheral nerves - low amt acid fast bacilli - high T cell mediated immunity - low humoral immunity
36
lepromatous leprosy spectrum? - acid fast bacilli? - Th1 CMI? - Th2 humoral immunity?
- high amt acid fast bacilli - low T cell mediated immunity - high humoral immunity, causes tissue damage
37
diagnosis of M leprae?
- acid fast stain of tissues - lepromin skin test - serology for PLG-1: phenolic glycolipid 1 - adhesin
38
drug therapy for m leprae?
dapsone: inhibits folic acid synthesis, check G6PDH
39
- reservoir: birds, mammals, soil, water - transient colonization - opportunistic pathogen (AIDS) - multidrug combos: clarithromycin/azithrmycin, ethambutol, rifabutin
MAC
40
- tuberculosis like disease - water and milk - midwest and TX
m. kansasii
41
waterborne, subQ abscesses and skin ulcers
m. marinum
42
- gram positive, catalase positive aerobic actinomycetales - form hyphae - ubiquitous in decaying organic matter - immunocompromised, avoid phagocytic killing due to secretion of catalase and SOD - survive and replicate in macrophages, block phagosome lysosome fusion - bronchopulmonary disease
nocardia
43
painless firm subcutaneous nocules
actinomycotic mycetoma
44
nodules along lympatics
lymphocutaenous disease
45
diagnosis of nocardia?
- gram positive, partially acid fast - aerial hyphae - antibiotic treatment: TMP-SMX

Infectious Disease (22 decks)

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