Mycobacterium Tuberculosis Flashcards Preview

Medical Microbiology > Mycobacterium Tuberculosis > Flashcards

Flashcards in Mycobacterium Tuberculosis Deck (24):
1

Major component of MTB cell wall?

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

2

What contributes to clumping of MTP?

Hydrophobicity

3

What is the incubation time of MTB?

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

4

Characteristics of MTB

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

5

Virulence factors

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

6

Natural history of MTB

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

7

How is MTB spread?

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

8

What happens to start primary infection?

Spread to hilar lymph nodea

9

How does latent TB occur?

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

10

Ghon complex

Hilar lymph node caseation and subpleural granulomas.

11

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

90%

12

Are patients with latent TB contagious?

No.

13

How to diagnose latent TB?

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

14

How to treat latent TB?

Isoniazid for 9 mos.

15

What is the key histological sign of MTB?

Caseating granulomas (caseous necrosis)

16

Symptoms of active TB

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

17

Does TB only occur in the lung?

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

18

Miliary vs cavitary TB

Miliary is nodular, cavitary is cavitary

19

How to stain TB?

Acid-fast

20

Pott's disease?

Vertebral body TB

21

TB drug regimen

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

22

Rifampin

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

23

Isoniazid

Prodrug that blocks mycolic acid synthesis. Hepatoxic.

24

Ethambutol

blocks polysaccaride synthesis in cell wall.