Tuberculosis

Question 1

what stain is used to detect mycobacterium tuberculosis

Answer 1

acid-fast

Question 2

shape

Answer 2

• rods (bacilli)
• gram-positive cell wall structrue but stain very weakly with gram stain

Question 3

complex cell wall rich in lipids called

Answer 3

mycolic acids

Question 4

the acid-fast cell wall has a resistance to

Answer 4

detergents, many antibiotics, and drying conditions

Question 5

acid fast cell wall functions

Answer 5

protection from lysis after phagocytosis
* blocks fusion of phagosome with lysosome
* masks PAMPS on the bacterial surface
* capacity for intracellular growth within macrophages –> “facultative intracellular pathogen”

Question 6

reservoir

Answer 6

human

Question 7

transmission

Answer 7

respiratory droplet nuclei

Question 8

high or low infectious dose

Answer 8

low

Question 8

high or low infectious dose

Answer 8

low

Question 9

populations at greatest risk for TB

Answer 9

• HIV+
• diabetics
• substance abusers
• low body weight/malnourishment
• immunocompromised

Question 10

pathogenesis (steps 1-3)

Answer 10

1. acid fast bacilli are inhaled and spread to alveoli
2. phagocytized by alveolar marcophages
3. M. tuberculosis capsule and waxy mycoliv acids block pahgosome form fusing with lysosome to avoid destruction within macrophages

Question 11

pathogenesis (steps 4-6)

Answer 11

4. Mycobacteria mulitply in macrophages (intracellular pathogen). Inflammatory response –> other phagocytes are attracted to the site
5. macrophages fuse together to form giant multinelceated cells
6. A granuloma (aka a tubercle) forms

Question 12

active secondary TB disease (step 7 of pathogenesis)

Answer 12

suppressed cell mediated immunity –> macrophages in tubercle die –> mycobacteria, enzymes, cytokines released –> forming area of necrosis
* tubercle ruptures, releases live mycobacteria into airways
* causes large defect called tuberculous cavity
* can be transmitted by coughing

Question 13

active TB signs and symptoms

Answer 13

• chronic cough
• bloody rust-colored sputum
• high fever
• night sweats
• weight loss
• fatigue

Question 14

miliary TB

Answer 14

when TB gets into ciruclation and spreads systemiclaly to all parts of the body

Question 15

2 ways TB can develop in HIV-infected person

Answer 15

• pesron with LTBI becomes infected with HIV and then develops TB disease as the immune system is weakened
• person with HIV becomes infected with M. tuberculosis and then rapidly develops TB disease

Question 16

Skin test for exposure to TB

Answer 16

tuberculin (Mantoux)

Question 17

what does the tuberculin test do

Answer 17

purified protein derivatives from the Mtb bacterium are inserted intradermaly and read 48-72 laters

Question 18

lab detection of mycobacteria

Answer 18

acid-fast bacilli (AFB) in sputum
* slow growth, 4-6 weeks

Question 19

prevention

Answer 19

BCG TB vaccines

Question 20

BCG TB vaccine

Answer 20

contains a live attenuated BCG strain
* Bacille Calmatte-Guerin
* BCG is a strain of mycobacterium bovis

Question 21

treatment

Answer 21

• people w/ LTBI can be given treatment to prevent them from developing TB disease
• combination of antibiotic therapy taken everyday for 6 months for uncomplicated TB, otherwise 12-18 months is standard and even longer if MDR-TB strain