4A - Tuberculosis

Question 1

Mycobacterium bovis

Answer 1

eradication (program, pasteurization, white tailed deer)

Question 2

Lipoarabinomannan

Answer 2

(LAM)
has immuno-regulatory and anti-inflammatory effects (inhibition of T-cell proliferation and macrophages)
Contributes to granuloma formation
Major virulence factor of Mycobacterium

Question 3

Cell mediated immunity

Answer 3

1 - antigen is processed and presented by macrophages
2 - activates T helper cells release cytokines to attract and activate more macrophages and cytotoxic T cells
3 - Cytotoxic T cells kill infected macrophages
4 - necrosis of tissue and formation of granuloma
(response to MTB - Immunocompetent/protective and lifelong, immunocompromised/host becomes ill)

Question 4

Method for detection of bovine tuberculosis

Answer 4

Caudal Fold Tuberculin (CFT) skin test

may not be responsive with severe pathology

Question 5

How CFT works

Answer 5

Tuberculin (purified cell wall protein from the bacteria) injected intradermally
Check CMI response after 72 hours (looking to visualize/measure inflammatory response)

Question 6

testing for TB by delayed exposure reason

Answer 6

The bacterium is slow growing, it takes time to develope an immune response (early tests may be negative)
Delay testing for 3-6 weeks following possible contact with an infected animal
The sensitivity of the test is less than 100% (eradiation of the disease requires multiple tuberculin tests)

Question 7

Sensitivity of a test

Answer 7

the percentage of true positive cases that are detected by the test. A test with 90% sensitivity will detect 90/100 cases.
10/100 cases will return a negative test even though they are positive

Question 8

Specificity of a test

Answer 8

the percentage of positive test cases that are truly infected. A test with 90% specificity will, on average, be false positive 10% of the time

Question 9

Granulomatous inflammation

Answer 9

the main feature of CMI
occurs in response to intracellular organisms that are very difficult for the host to destroy so that the inflammatory response itself tends to cause extensive tissue damage

Question 10

granuloma

Answer 10

a nodule of granulomatous inflammation

Question 11

TB granuloma

Answer 11

tend to be slow growing 
made up of big infected macrophages
multinucleated giant cells 
TH Cytokines attract more macrophages 
TC kill macrophages 
may be calcified, and surrounded by a fibrous tissue capsule and visible on radiographs

Question 12

caseous necrosis

Answer 12

happens to granulomas

breakdown of the granuloma leads to the release of the mycobacterium and infection of surrounding tissues

Question 13

military TB

Answer 13

What happens when bacteria spread via lymphatics and blood by migration of infected macrophages
The result is many small foci in bone, lymph, urogenital, mammary gland and lung
A type of disseminated TB

Question 14

Antimicrobials for TB

Answer 14

Rifampicin and Isoniazid

Question 15

Rifampicin

Answer 15

a quinolone antibotic that affects bacterial RNA polymerase (most important treatment)

Question 16

Isoniazid

Answer 16

very narrow spectrum of activity - prevents the formation of cell wall MYCOLIC acid
(synthetic antimicrobial, nicotinamide analog)