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Unit 2 Micobio > L14: mycobacterial infections > Flashcards

L14: mycobacterial infections Flashcards

1
Q

Mycobacterium tuberculosis morphology

A

Acid fast, mycolic acids, unusual lipids
Obligate aerobes
Slender slightly curved rod shaped bacillus
Non-motile

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2
Q

Mycobacterium tuberculosis virulence factors

A

NO classic virulence factors or toxins

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3
Q

Agents that cause TB infection

A

Mycobacterium tuberculosis complex:

Mycobacterium tuberculosis: Human only reservoir: respiratory person-to-person

Mycobacterium bovis: cattle, consumption of unpasteurized milk, infected animals/humans

Mycobacterium africanum: west african countries, may be spread through food, opportunistic

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4
Q

higher risk for TB infection

A

prolonged exposure, crowded housing conditions, close contact, children infected by caregivers, alcoholism, IVDU, malnutrition, DM, immunosuppression, silicosis: pneumoconiosis (inhalation of silica dust)

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5
Q

mycobacterium tuberculosis infects

A

very old or very young, bimodal distribution, immunocompromised

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6
Q

TB presentation ins infants and immunocompromised

A

hematogenous dissemination→ meningitis, other sx

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7
Q

TB presentation in older patients

A

failure of immune system→ reactivation of latent infection

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8
Q

TB MOA

A

Droplets→ alveoli→ phagocytosis by macrophages→ prevents fusion with lysosomes while allowing nutrient containing vesicles to merge
Innate and cell-mediated host response→ self-destruction of cells and tissues

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9
Q

general symptoms of TB

A

insidious onset, nonspecific cough, weight loss, night sweats
Immune competent: confined to lungs, contained in a few weeks, most resolve TB infection

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10
Q

Immediate resolution of TB

A

cleared by alveolar macrophages, no active case of TB

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11
Q

Primary active TB

A

Restricted to lower lung, (+)skin test

granuloma→ +/- progression and calcification→ CXR: tubercles, ghon bodies

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12
Q

Progressive primary TB/Active TB

A

Immune system can’t stop bacteria from multiplying
One/both upper lobes involved
Contagious, exp: immunocompromised

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13
Q

Latent infection TB

A

Well patients with inactive TB bacteria
May be viable in lesions for long periods
No symptoms, not contagious

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14
Q

how to kill TB

A

pasteurization as they’re heat sensitive

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15
Q

Skin testing of TB

A

MTB protein derivative (PPD): Mantoux skin test

Measures size of induration after 48-72 hours

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16
Q

what’s a “booster”?

A

a person with past TB infection but minimal PPD reaction→ 2nd skin test

17
Q

why is TB difficult to stain/culture

A

Unusual lipids + mycolic acids

slow growth phenotype

18
Q

how to stain TB

A

Acid fast→ resist decolorization→ Ziehl-Neelsen or Kinyoun stains

19
Q

MTB

A

TB test: stimulates isolated T cell to produce IFN-gamma→ quantify

20
Q

GeneXpert

A

TB nucleic acid amplification test: presence of MTB and rifampin resistance

21
Q

non TB mycobacterial agents (2)

A

Mycobacterium avium Complex (MAC) and Mycobacterium kansasii

22
Q

Mycobacterium avium Complex (MAC) and Mycobacterium kansasii morphology

A

Weakly G+ aerobic bacilli
Acid fast
Slow growing
Opportunistic

23
Q

how MAC and MK presents in middle aged/older male smokers

A

cavitary lesions resemble TB

24
Q

how MAC and MK presents in Elderly female non-smokers

A

patchy or nodular CXR

Lady windermere’s syndrome

25
Q

other MAC and MK presentation

A

Solitary pulmonary nodule

26
Q

how MAC and MK presents in AIDs patients

A

Disseminated disease: no organ spared

HAART and abx prophylaxis→ less infections

27
Q

how to definitively identify MAC/MK

A

PCR for 16S rRNA sequence

28
Q

MAC/MK on culture

29
Q

MAC and MK are spread by

A

Any water source, soil, plants: ingestion

NO person-to-person transmission: no isolation required

30
Q

Mycobacterium abscesses

A

Especially in cystic fibrosis: drug resistance=hard to treat

Rare in normal population

31
Q

Cell wall of TB

A

peptidoglycan layer
Mycolic acids
Lipoarabinomannan
Cord factor

32
Q

Mycolic acids

A

long chain fatty acids prevent dehydration, resist H2O2

33
Q

Lipoarabinomannan

A

mycoside: glycolipid mycolic acid + disaccharide

34
Q

Cord factor

A

inhibits cell mediated immunity, scavenges reactive oxygen intermediates (ROI)

35
Q

Insidious TB reactivation

A

cough, weight loss, ever, fatigue, night sweats, chest pain

36
Q

Lesions in TB reactivation

A

caseous lesions with necrosis→ erosion→ discharge TB bacilli into bronchi→ contagious

37
Q

Miliary TB reactivation

A

Erode blood vessels→ hematogenous spread to other body sites: any organ→ miliary TB (massive spread)

Unit 2 Micobio (9 decks)

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