Mycobacterium Tuberculosis Lecture 10

Question 1

Structure

Answer 1

• Obligate aerobe, acid fast bacilli

- Mycolic Acid retains carbol fuschin

Question 2

Virulence Factors

Answer 2

• Cord factor interferes with mitochondria and inhibits phagocyte trafficking
• Sulfatides prevent the fusion of the phagolysosome

Question 3

Incidence

Answer 3

-Rising since HIV, can be latent or active, presents like pnemonia with a positive skin test

Question 4

Testing

Answer 4

-Skin test, 5mm induration for high risk individuals such as those with previous positive diagnosis and HIV patients, recent exposure
-10 mm: Healthcare workers, recent converters, immigrants, children
-15mm: rest of the population
X Rays can make definitive diagnosis and show active TB

Question 5

Treatment

Answer 5

• Latent: Isoniazid for 9 months
• Active: Isoniozid, Rifampin, Pyridaxalone, Ethambutol and isolation
• Never add one drug

Question 6

Prognosis

Answer 6

• Most patients go into a latent stage and set up a granuloma that isn’t broken
• 15% can have a breakage of the granuloma at some point during immunosupression

Question 7

Drug Side Effects

Answer 7

-Isoniazid is hepatotoxic and monitoring of liver enzymes is important.

Question 8

Growth

Answer 8

-Slow growers, so mutations are highly possible and culture is difficult. Obligate intracellular microbe

Question 9

Issues with testing

Answer 9

• Booster effect: negative tests boost immunity in those who have a waning immune system
• BCG vaccine does not factor into reading skin test because immunity often wanes with vaccination.
• Other mycobacterium could cause a positive test, important to confirm.