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Tim's CP Board Review > Mycobacteriology > Flashcards

Mycobacteriology Flashcards

1
Q

Mycobacterium tuberculosis complex

A 
MTB
Africanum
Bovus (including BCG)
Canetii
Microti
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2
Q

Mycobacterial drug resistance patterns

A

MDR: resists isoniazid and rifampin
XDR: MDR, also resists second-line drugs (aminoglycoside, quinolone)
TDR: Totally resistant…

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3
Q

TB treatment

A

RIPE: Isoniazid, rifampin, ethambutol, pyrazinamide.
1st-line. Treat for 4-6 months

2nd-line: Add a fluoroquinolone or aminoglycoside

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4
Q

Slow-growing photochromogens

A

Pigmented with light, not pigmented without.

Kansasii
Marinum
Szulgai (if grown cold)

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5
Q

Slow-growing scotochromogens

A

Pigmented regardless of light exposure

Gordonae
Scrofulaceum
Szulgai (if grown warm)

*Xenopi?

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6
Q

Slow-growing non-chromogens

A

MAC
Haemophilum
Simiae

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7
Q

Mycobacterial stains

A

Ziehl-Neelsen: Heating step.
Kinyoun: No heating. Standard.
Modified acid-fast: Weaker decolorizer. eg, Fite stain. For Nocardia, Leprae
Auramine fluorochrome: For direct/rapid visualization

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8
Q

Nocardia

A

Filamentous/branchine beaded bacteria.

Gram-positive. Modified fite stain positive

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9
Q

Lab workup of mycobacteria.

A

Start with AFB smear and direct visualization (flurochrome). If positive, do NAT to ID and culture for sens.

Always also culture (liquid brother with solid agar backup). Follow positive results with DNA probes to identify MTB complex members. Can also use MALDI, NGS, or biochem methods for final identification

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10
Q

Molecular identification of mycobacterial species

A

rpoB gene (qPCR? sequencing?)

IS6110 RFLP analysis

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11
Q

Mycobacterium bovis

A

MTB complex. Slow growing non-chromogen. Smooth colonies.

Causes abdominal infections (often mass-forming). Dairy.

Negative for niacin, nitrate. TCR sensitive. Resists pyrazinimide.

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12
Q

Mycobacterium avium complex

A

1 cause of nontuberculoidal pulm disease. Can cause scrofula. Whipple-like gastrointestinal disease in the immunocompromised.

Slow-growing non-chromogen.

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13
Q

Mycobacterium haemophilum

A

Slow-growing non-chromogen.

Needs iron supplementation to grow

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14
Q

Mycobacterial culture media

A

Lowenstein-Jensen (egg-based, old), Middlebrook (7H10, 7H11)

Broths (standard, based on middlebrook formulas)

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15
Q

Mycobacterium leprae

A

Cannot be routinely cultured. Has tropism for cooler tissues. Armadillos.

Diagnose with lepromin skin test (if immunocompetent) or direct skin biopsy.

Response patterns may be lepromatous (ineffectual, disfiguring) or tuberculoid (effective; paucicellular)

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16
Q

TB testing

A

PPD: 10mm normal response, 5mm in immunocompromised

IGRA: Peripheral lymphocyte release in contact with various mycobacterial antigens.

17
Q

Fast-growers

A

Chelonae
Fortuitum
Abscessus

18
Q

Mycobacterium kansasii

A

Slow-growing photochromogen

Causes systemic disease.

Nitrate positive.

19
Q

Mycobacterium marinum

A

Slow-growing photochromogen. Prefers colder temperatures.

Causes skin infections in association with marine life (fish-tank granuloma).

Lymphangitic spread.

20
Q

Mycobacterium scrofulaceum

A

Slow-growing scotochromogen

Causes scrofula (cervical LAD), usually in children.

21
Q

Mycobacterium tuberculosis

A

Rough colonies.

Niacin+, nitrate+, resistant to TCH but susceptible to NAP/PNB. Trehalose accumulates in cords in agar.

22
Q

Mycobacterium xenopi

A

Slow-growing scotochromogen? Prefers hot temperatures (42-45C).

Causes pulmonary disease.

Arylsulfatase+. “Birds-egg nest” colonies

23
Q

Mycobacteria in cystic fibrosis patients

A

When culturing pulmonary samples, must add oxalic acid to inhibit growth of pseudomonas

24
Q

Mycobacterium chelonae

A

Fast-grower.

Citrate+. Salt-susceptible.

25
Q

Mycobacterium fortuitum

A

Fast-grower.

Nitrate+. Salt-resistant.

26
Q

Mycobacterium abscessus

A

Fast-grower.

Salt resistant.

27
Q

Mycobacterium ulcerans

A

Produces “mycolactone” toxin which causes ulceration

28
Q

Nonpathogenic mycobacterial species

A

Gordonae
Lentiflavum
Mucigenicum
Terrae

Tim's CP Board Review (16 decks)

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