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Infectious Disease > Mycobacteria and Nocardia > Flashcards

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

A

scrofula

24
Q

dx of TB with radiology reveals lesions where?

A

oxygenated parts of lungs

25
Q

tuberculin (mantoux) skin test is a _______ hypersensitivity response, which screens for ____ TB by injecting _________

A

type IV delayed

latent

Purified protein derivative

26
Q

in mantoux TB skin test, redness swelling and induration occur after _____ days, and patients are not positive until ______ weeks after infection

A

2-3 days

3-6 weeks

27
Q

when reading tuberculin test, measure ______ only

A

induration

28
Q

limitations of PPD tuberculin test?

A

anergy (Esp with HIV patients), recent TB infection, very young age, prior immunization, cross reactivity to other mycobacteria

29
Q

alternative to tuberculin test for diagnosis of latent TB, measures M. tb antigens, more specific

A

IGRA: interferon gamma release assay

30
Q

diagnosis of M. tb?

A
  • 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
Q

first line drugs for TB active disease?

A

isoniazid (inhibits mycolic acid synthesis), rifampin, streptomycin, pyrazinamide, ethambutol (inhibits arabinoglactan synthesis)

32
Q

candidates for TB prophylaxis?

A

positive tuberculin skin test + HIV infection, close contacts with infectious TB, chext Xray with previous TB, injection drug use

33
Q

BCG vaccine contains live attenuated ________, most effective in children, but not recommended in US b/c it affects ________

A

M. bovis

surveillance

34
Q
  • transmission by aerosols, contact
  • obligate intracellular pathogen
  • infects skin, peripheral nerves (Schwann cells), eyes, mucous membrane, testes
  • reservoir: humans, primates, armadillos
A

M. leprae

35
Q

tuberculoid leprosy spectrum

  • nerve damage?
  • acid fast bacilli?
  • Th1 CMI?
  • Th2 humoral immunity?
A

2-40 yr incubation, neuropathies and enlarged peripheral nerves

  • low amt acid fast bacilli
  • high T cell mediated immunity
  • low humoral immunity
36
Q

lepromatous leprosy spectrum?

  • acid fast bacilli?
  • Th1 CMI?
  • Th2 humoral immunity?
A
  • high amt acid fast bacilli
  • low T cell mediated immunity
  • high humoral immunity, causes tissue damage
37
Q

diagnosis of M leprae?

A
  • acid fast stain of tissues
  • lepromin skin test
  • serology for PLG-1: phenolic glycolipid 1 - adhesin
38
Q

drug therapy for m leprae?

A

dapsone: inhibits folic acid synthesis, check G6PDH

39
Q
  • reservoir: birds, mammals, soil, water
  • transient colonization
  • opportunistic pathogen (AIDS)
  • multidrug combos: clarithromycin/azithrmycin, ethambutol, rifabutin
A

MAC

40
Q
  • tuberculosis like disease
  • water and milk
  • midwest and TX
A

m. kansasii

41
Q

waterborne, subQ abscesses and skin ulcers

A

m. marinum

42
Q
  • 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
A

nocardia

43
Q

painless firm subcutaneous nocules

A

actinomycotic mycetoma

44
Q

nodules along lympatics

A

lymphocutaenous disease

45
Q

diagnosis of nocardia?

A
  • gram positive, partially acid fast
  • aerial hyphae
  • antibiotic treatment: TMP-SMX

Infectious Disease (22 decks)

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