Tuberculosis Flashcards
Where are the bulk of uk TB cases and why?
39% are in london because it has a high immigration from high incidence countries.
What causes TB?
Mycobacterium Tuberculosis
Mycobacterium Bovine
Among others.
TB causing organisms are AAFBs, what does this mean?
Acid-Alcohol fast bacilli.
It means they dont decolourize in acid or alcohol during staining techniques, they are also often resistant to absorping the dye.
We use a ZN stain for them.
Why cant our body overcome TB?
The mycobacteria are resistant to macrophages and neutrophils.
How is TB spread?
Droplets of M. Tuberculosis form when someome sneezes/coughs and hang around in the air for a long time.
M. Bovis is spread by infected cow’s milk and deposited into the cervical & intestinal lymph nodes.
How does TB occur?
The invading mycobacterium trigger Th1 cells which activate macrophages.
Macrophages, epithelioid cells and langhan’s giant cells accumulate around the infection and form granulomas.
Then central caseous necrosis begins.
How does a primary TB infection affect the body?
Often asymptomatic but can have fever, malaise, erythema nodosum and chest signs.
Spread from alveoli -> Hilar lymph nodes -> blood to all organs.
How does a primary TB infection resolve?
85% reach a primary complex then heal (initial lesion and lymph node).
Can be progressive, latent or cleared.
What can happen if primary TB progresses?
Primary focus can enlarge and cavitate while hilar lymph nodes compress the bronchi and eventually cause lobar collapse and discharge into the bronchus leading to T. Bronchopneumonia.
Or 6-12 months later:
- Miliary TB, a fine mottling of small granulomata all over a CXR
- Meningeal TB, high protein CSF & high lymphocyte count
- T. Pleural Effusion
What does post-primary TB refer to?
Reactivation of latent infection or reinfection after original disease. Can affect just about any tissue
What are the symptoms of post primary pulmonary TB?
Cough with sputum and haemoptysis Pleuritic chest pain SOB Malaise & Weight Loss Fever & Night Sweats
Maybe crackles/bronchial breathing
What are the risk factors for post primary pulmonary TB?
History of diabetes, immunosuppression or TB.
Immunosuppresive Drugs
History of alcohol, IV drug abuse, poor living standards.
Immigration from a high risk area.
How do we investigate a case of TB?
Look for 3 positive sputum specimens on successive days.
CXr for patchy shadowing in upper zones and cavitation. Calcification if chronic or healed TB.
CT, bronchoscopy and pleural aspiration/biopsy.
What must we do on finding a TB case?
Notify and refer to TB specialists.
Why do we HIV test TB sufferers form areas of high HIV incidence?
Because the immunocompromised often get TB so there’s a high chance they’re susceptible because of underlying HIV.
