Week 2: Mycobacteriology Flashcards

1
Q

Mycobacteria pathogen type

A

Intracellular pathogens

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2
Q

Mycobacteria capsule type?

A
  • Lipid and polypeptide capsule
  • not stained by Gram stain due to mycolic acid & lipids in cell wall
  • Stain is resistant to decolorization by acids (acid fast)
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3
Q

Mycobacteria stains

A
  • Ziehl-Nielson
  • Kinyon
  • Fluorochrome
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4
Q

Mycobacteria culture media

A
  • Lowenstein-Jensen
  • Middlebrook agar
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5
Q

Mycobacteria gram stain

A

not stained by gram stain due to mycolic acid & lipids

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6
Q

Mycobacteria growth speed

A

Slower growth than other bacteria

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7
Q

Mycobacteria acid-fast meaning

A

not easily decolorized by acids (as when stained) —used especially of bacteria and tissues.

Stain is resistant to decolorization by acids (Acid-fast)

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8
Q

Mycobacterium tuberculosis metabolism type

A

Obligate aerobe

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9
Q

Mycobacterium tuberculosis unique characteristics

A

prevents the fusion of phagosome with lysosomes (can survive in macrophages)

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10
Q

Mycobacterium tuberculosis culture time

A

~6 weeks

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11
Q

Mycobacterium tuberculosis transmission mechanism

A

Inhaled aerosol

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12
Q

Mycobacterium tuberculosis prevention

A

N95 mask

Airborn isolation

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13
Q

Mycobacterium tuberculosis infection types

A
  • Latent infection: diagnosis ppd or IGRA
  • Active disease: smear & culture, TB cord factor; PCR
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14
Q

Pertinent strains of mycobacterium

4 listed

A
  • Mycobacterium tuberculosis
  • Mycobacterium avium-intracellulare
  • Mycobacterium scofulaceum
  • Mycobacterium marinum
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15
Q

Mycobacterium tuberculosis

A

Causes TB and is often resistant to multiple drugs

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16
Q

Mycobacterium avium-intracellulare

A
  • causes disseminated, non-TB disease in AIDS
  • often resistant to multiple drugs\
  • prophylaxis with azithromycin when CD4+ count < 50 cells/mm3
17
Q

Mycobacterium scrofulaceum causes

A

cervical lymphadenitis in children

18
Q

Mycobacterium marinum causes

A

hand-infection in aquarium handlers

19
Q

All mycobacteria are?

A

Acid-fast pink rods

20
Q

TB symptoms

A
  • fever
  • night sweats
  • weight loss
  • cough (nonproductive or productive)
  • hemoptysis
21
Q

Virulence factors of mycobacterium

A
  • cord factor creates a serpentine cord appearance in virulent M tuberculosis strains; activates macrophages (promoting granuloma formation) and induces the release of TNF-α
  • Sulfatides (surface glycolipids) inhibit phagolysosomal fusion
22
Q

TB and PPD

A

PPD + if current infection or past exposure

PPD - if no infection and in sarcoidosis or HIV infection (especially with low CD4+ cell count)

23
Q

Fewer false positives of TB after BCG vaccination

A

Interferon-γ release assay (IGRA) has fewer false positives from BCG vaccination

24
Q

What is the BCG vaccine?

A

Bacillus Calmette–Guérin vaccine is a vaccine primarily used against tuberculosis. In countries where tuberculosis or leprosy is common, one dose is recommended in healthy babies as close to the time of birth as possible.

25
BCG vaccine false positives
* Vaccination with BCG may cause a false positive reaction to a TB skin test. A positive reaction to a TB skin test may be due to the BCG vaccine itself or due to infection with TB bacteria. ... TB blood tests are the preferred method of TB testing for people who have received the BCG vaccine. * IGRA has fewer false positives for those who have received the BCG vaccine
26
Histological features of TB
Caseating granulomas with central necrosis and Langerhans Giant cells (characteristic of 2o tuberculosis as shown in picture)
27
Describe the course of a TB infection