Mycobacterium Tuberculosis

Question 1

What is the process from inhaling TB and it being phagocytosed?

Answer 1

1. TB particle inhaled
2. LAM on TB surface binds to receptors on pulmonary macrophage to encourage phagocytosis
3. TB particle is phagocytosed

Question 2

What are the steps in which TB forms a granuloma?

Answer 2

4. TB resists lysis by lysosyme
5. TB survives within macrophage, mast cells are stimulated to release TNFalpha, recruiting macrophages and neutrophils which all travel to the lymph nodes
6. T cell proliferation and differentiation occurs
7. T cells travel to areas altered by chemokines
8. T cells interact with the TB-infected macrophages and TNFalpha forming a granuloma

Question 3

What is a granuloma?

Answer 3

A necrotic centre surrounded by multinucleated macrophages and on the outside T cell controlling those macrophages

Question 4

What are some features that suggests that a host is carrying TB?

Answer 4

1. Pulmonary TB
2. Acid fast bacilli in stains of sputum
3. Cavitation visible on chest x-ray
4. Cough
5. Fails to cover mouth when coughing
6. Delay in diagnosis

Question 5

What are the three varieties of mycobacteria?

Answer 5

1. mycobacterium tuberculosis group
2. non-tuberculous mycobacteria
3. leprosy

Question 6

How is TB acid fast?

Answer 6

It retains its red stain when decolourised due to its cell wall which is rich in lipids

Question 7

What are the two possible scenarios for when the immune system manages to contain TB?

Answer 7

The bacteria dies off of natural causes

It is a latent infection which can be reactivated by age, steroids, cancer or anti TNFalpha drugs

Question 8

What is the mantoux test?

Answer 8

Patient injected with TB protein under the skin

72 hours later if reactive lump appears then the person is hypersensitive to TB antigen

Question 9

What are some problems with the mantoux test?

Answer 9

Some people don’t recat
Takes three days
People who have had BCG vaccine give a false positive
Doesn’t tell if you currently have or just previouslt have had TB

Question 10

What are the four main TB drugs?

Answer 10

Rifampicin (kills RNA)
Isoniazid (targets cell wall)
Pyrazinamide (gets into granuloma)
Ethambutol (helps against drug resistance)
(only three needed to treat TB)

Question 11

How should TB be diagnosed?

Answer 11

1. Suspicion
2. Chest X-ray
3. Sputum specimens
4. TB PCR
5. TB culture

Question 12

How should TB be managed?

Answer 12

1. Get better (RIPE)-shortest dose is 6 months

2. Prevent transmission (isolation/respirator masks/antibiotics until not infectious)