Tuberculosis Flashcards
1
Q
Epidemiology
- Percentage of population that carry M. tuberculosis
- Percentage of those infected that develop disease in their lifetime
A
- 1/3
- 10%
2
Q
Route of transmission
A
Inhalation of bacilli in aerosolised droplets from a person with active disease
3
Q
Risk factors for tuberculosis (2 main categories)
A
- Living and working conditions
- Infected contacts
- Asian and African countries
- Homelessness, overcrowding
- IV drug use
- Alcoholism
- Immunocompromise
- HIV
- Smoking
- Silicosis
- Diabetes
- Malnutrition
- Steroids
- Immunosuppressants
- Babies and young children
4
Q
Aetiological organism
- Features of cell wall and the significance of this
- Aerobic / anaerobic
- Intracellular / extracellular
- Staining and shape
- Rate of growth
A
Mycobacterium tuberculosis
- Mycolic acid creates a thick, waxy, lipid-rich cell wall - resists killing by oxygen free radicals inside phagolysosome
- Aerobic
- Intracellular
- Acid-fast bacillus (red on Ziehl-Neelson stain and resists destaining with acid). Stains weakly positive on gram stain
- Slow-growing
5
Q
Formation of granulomas (5 steps)
A
- Macrophages secrete IL-12 to activate TH1 cells
- Lymphocytes surround infected macrophages
- Other macrophages fuse with infected macrophage, making a giant multinucleated cell
- Bacilli inside resist immune response
- Abnormal central cell death causes caseous necrosis
6
Q
Symptoms of pulmonary tuberculosis
A
- Chronic cough (dry → mucoid → purulent → bloody)
- Fever, night sweats, chills, weight loss, fatigue
- Chest pain and dyspnoea
7
Q
Signs of pulmonary tuberculosis
A
- Dullness on percussion
- Decreased fremitus
- Crackles
- Clubbing
8
Q
Investigations for tuberculosis
A
- CXR
- Focal infiltration, Gohn focus
- Calcification, cavitation, fibrosis, lymph node enlargement
- Sputum samples
- 3 mornings in a row
- Acid fast, microscopy, culture and sensitivities
Other tests
- Bronchoscopy, pleural tap
- HIV serology
- Mantoux and Quantiferon (latent TB - less useful)
9
Q
Management of active tuberculosis
A
First 2 months (IPREP)
- Isoniazid + pyridoxine
- Rifampicin
- Ethambutol
- Pyrazinamide
Next 4 months
- Isoniazid
- Rifampicin
10
Q
Extrapulmonary tuberculosis
- High risk group
- Organs affected
- Type of TB caused by haematogenous spread (disseminated)
A
- Immunosuppressed persons
- Almost any organ can be affected
- Pleura (tuberculous pleurisy)
- Meninges (tuberculous meningitis)
- Lymph nodes (lymphadenopathy)
- Urogenital (urogenital tuberculosis)
- Bone (Pott disease of the spine, osseous tuberculosis - osteomyelitis)
- Miliary TB
- Millet lesions seen on CXR
- Accounts for 10% of extrapulmonary cases
11
Q
Drug side effects
- Isoniazid
- Rifampicin
- Ethambutol
A
- Isoniazid - peripheral neuropathy and hepatitis
- Rifampicin - red tears/urine and hepatitis
- Ethambutol - colour blindness (optic neuritis)
