Tuberculosis

Question 1

What bacteria causes TB and what are the other types of similar bacteria?

Answer 1

Mycobacterium tuberculosis

NTBs can be rapid growing, non rapid growing and other. eg leprosy

Question 2

How is TB spread and what are transmission risk factors?

Answer 2

Pulmonary route

normal so age, immune suppressed, household contact. Main ones are institutional workers and health care workers.

Question 3

What is unique about TB appearance?

Answer 3

It is an acid fast bacillus, it retains red CF stain (due to wall being rich in mycolic acids). Ziehl Neelsen stain.

Question 4

What is the pathogenesis of TB?

Answer 4

Tb inhaled and lodges in distal airways eg alveolus
Alveolar macrophage ingests Tb bacteria
Bacteria will resist lysis:-
-LAM will prevent macrophage apoptosis and blocks antigen presentation. Before ingested binds and causes ingestion/
-Alters vesicle formation
-tough cell wall
Macrophage with bacteria in them activates mast cells, causing TNF alpha release, recruiting neutrophils, macrophages and Dendritic cells.
Dendritic cells go to lymph node, and stimulate T cells (IL-12 and IL-2).
T cells traffic to infecton site ( where activated epithelium are)
Granuloma forms, T cells cause macrophage maturation to epitheloid ones. Necrotic centre with epitheloid macrophages surrounding centre with T cells sustaining them.

Question 5

What can primary TB infection cause?

Answer 5

Pleural infection, bronchopneumonia, cavitation

Question 6

How is TB diagnosed?

Answer 6

Chest X-ray; sputum for afb; suspicion; TB PCR; Mantoux test; Quantiferon gold

Question 7

How could TB be reactivated?

Answer 7

Rheumatoid arthritis ( anti TNF alpha drugs). HIV

Question 8

What are the main TB drugs?

Answer 8

Rifampcin (RNA target); isoniazid (mycolic acid target); ethambutol