Tuberculosis Flashcards
What causes TB?
Mycobacterium Tuberculosis
Mycobacterium Bovine
Among others.
What is mycobacterium tuberculosis
Non-motile bacillus
Slow growth
Aerobic- predilection for APICES of lung
TB causing organisms are AAFBs, what does this mean?
Acid-Alcohol fast bacilli.
Don’t decolourise in acid or alcohol during staining techniques
Often resistant to absorbing the dye
ZN stain is used
Why cant our body overcome TB?
The mycobacteria are resistant to macrophages and neutrophils.
How is TB spread?
Airborne - pulmonary & laryngeal spreads
M. Bovis spread by infected cow’s milk
Deposited into the cervical & intestinal lymph nodes.
How does TB occur?
Invading mycobacterium trigger Th1 cells which activate macrophages.
1. Macrophage activation-> epithelioid cells-> Langhan’s giant cells
2. Indigestible material produces Granuloma
3. Central caseating necrosis
(Caseating Necrosis = causes tissues to become “cheese-like” in appearance)
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 happens when primary infection progresses to tuberulous bronchpneumonia
Primary focus enlarges- cavitation
Enlarged hilar l.n compress bronchi- lobar collapse
Enlarged l.n discharges into bronchus
What is miliary TB
Hematgenous spread of bacteria to multiple organs
Fine mottling on X-ray
Widespread granulomatoma
CNS TB in 10-30%
What does post-primary TB refer to?
Infection after latent disease
Reinfection after original disease
Can affect almost any tissue
What are the symptoms of post primary pulmonary TB?
Cough with sputum and haemoptysis
Pleuritic chest pain
SOB
Malaise and Weight Loss
Fever and Night Sweats
Maybe crackles/bronchial breathing
What are the clinical symptoms of TB
Cough
Fever (absent in 37%)
Night Sweats (absent in 39%)
Weight loss (absent in 38%)
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.
What other ways could you investigate TB
- 3 sputum samples, 8-24 hours gap, at least 1 early morning sample
- Induced sputum
- Bronchoscopy with BAL
- EBUS w/ biopsy
- Lumbar puncture in CNS TB
- Urine in urogenital TB
- Aspirate/ biopsy from tissue
How would you diagnose active pulmonary TB
CXR
Mediastinal lymphadenopathy(mainly unilateral)
Pleural effusion
Miliary
Pneumonic lesion with enlarged hilar nodes
How do we investigate a case of post-primary TB?
CXR
Apices, soft fluffy/nodular upper zone
Lymphadenopathy
When may you use a CT scan
- Normal CXR but clinical suspicion
- Miliary TB
- Cavitation
- Lymphadenopathy
- Targets for BAL (Broncho alveolar lavage)
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?
Immunocompromised often get TB
High chance they’re susceptible because of underlying HIV
Why do we use multi-drug therapy for TB?
TB very quickly grows drug resistant to single agent treatment
What drugs do we use to treat TB?
0-2 months - Rifampicin, Isoniazid, Pyrazinamide & Ethambutol
2-6 months - Rifampicin & Isoniazid
What are the side effects of ethambutol
Optic neuropathy
What are the side effects of pyrazinamide
Gout
