Flashcards in Tuberculosis - aetiology, pathogenesis and pathological features Deck (14)
Describe the sequence of events in cells/tissues after infection with TB
Spread to lymph nodes
Bacteraemia - organisms divides unchecked
-Inhibition of lysosomal fusion
What are the sequences of events in TB infection, starting with inhalation
-Inhalation of the bacilli
-Implants in lower part of upper lobe of the lung, or upper part of the lower lobe
-Develops a Ghon focus, which undergoes central caseous necrosis
-Bacilli drain to regional lymph nodes, that also caseate, forming more Ghon processes
-At this stage, there is haematogenous and lymphatic dissemination
-Ghon complexes undergo fibrosis and form a Ranke complex
What are clinical manifestations of primary TB?
Progressive lung disease with:
-Malaise, weight loss
-Fever, night sweats
- Resembles acute bacterial pneumonia in some cases
What % of TB deaths occur in low income countries?
How many times more likely are you to get TB in Australia if you are Aboriginal, compared to non-aboriginal?
Is Tb aerobic or anaerobic?
Describe some TB testing
- Sputum, tissue ZNs stain, fluorescent staining
What are 3 virulence factors of Mycobacterium tuberculosis?
-Cord factor - a glycolipid in the cell wall
-Inhibition of phagolysosome formation
-Suppression of T-cell function
-Protection against complement activated killing
What does secondary TB infection look like clinically?
Involves apex of the lung. Due to pre-existing hypersensitivity, there is little enlargement of the hilar lymph nodes
Tissue necrosis with cavitation is evident
What type of inflammation do you see in TB?
Describe progressive pulmonary TB
Extension of the lung lesion, cavitation with central caseation that is not walled off by fibrous tissue
This erodes into bronchi and blood vessels, becoming 'open TB'
The disease spreads through the blood and lymph nodes
Describe Miliary TB
After dissemination through the lymph nodes, bacilli in venous blood get back to the lungs, and cause numerous small lesions throughout the lung
Where can you get TB developing?