Mycobacterium Tuberculosis Flashcards

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1
Q

Major component of MTB cell wall?

A

Mycolic Acid, lipid rich, so resistant to traditional stains/antibiotics.

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2
Q

What contributes to clumping of MTP?

A

Hydrophobicity

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3
Q

What is the incubation time of MTB?

A

Very slow, 12-24 hours. Takes about 4-6 weeks to visualize colonies.

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4
Q

Characteristics of MTB

A

Non-motile, non spore-forming aerobic bacilli. Gram null but stain with an acid fast stain.

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5
Q

Virulence factors

A

No toxins or capsules, just intracellular survival. Inhibition of phagosome-lysosome system

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6
Q

Natural history of MTB

A

Transmission, primary tuberculosis with cavitary lesions, then latent TB, can reactivate.

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7
Q

How is MTB spread?

A

Small droplet nuclei that can remain suspended in air for several hours. These penetrate alveoli and are ingested by alveolar macrophages

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8
Q

What happens to start primary infection?

A

Spread to hilar lymph nodea

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9
Q

How does latent TB occur?

A

Immune system contains primary infection and a granuloma is formed. MTB persist within inactivated macrophages within the granuloma.

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10
Q

Ghon complex

A

Hilar lymph node caseation and subpleural granulomas.

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11
Q

Latent TB is the endpoint of primary tb in ?% of patients

A

90%

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12
Q

Are patients with latent TB contagious?

A

No.

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13
Q

How to diagnose latent TB?

A

PPD or IGRA. IGRA not affected by the BCG vaccination.

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14
Q

How to treat latent TB?

A

Isoniazid for 9 mos.

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15
Q

What is the key histological sign of MTB?

A

Caseating granulomas (caseous necrosis)

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16
Q

Symptoms of active TB

A

Cough, hemoptysis, night sweats, anorexia, weight loss, weakness, dyspnea.

17
Q

Does TB only occur in the lung?

A

No, can occur in bones, LNs, brain, GI tract, kidneys, etc.

18
Q

Miliary vs cavitary TB

A

Miliary is nodular, cavitary is cavitary

19
Q

How to stain TB?

A

Acid-fast

20
Q

Pott’s disease?

A

Vertebral body TB

21
Q

TB drug regimen

A

Rifampin, Isoniazid, Pyrazinamide, Ethambutol for 2 months, then RIF and INH for 4.

22
Q

Rifampin

A

Inhibits DNA-dep RNA pol, induces hepatic p450 enzymes. Hepatotoxicity, thrombocytopenia.

23
Q

Isoniazid

A

Prodrug that blocks mycolic acid synthesis. Hepatoxic.

24
Q

Ethambutol

A

blocks polysaccaride synthesis in cell wall.