Mycobacterial diseases Flashcards
How are mycobacteria different to other bacteria?
- Unusual waxy cell wall (high lipid content)
- Slow growing
What staining characteristics are used for mycobacteria?
- Poor uptake of Gram stains
- Retain certain stains without decolourisation by acid/alcohol
- Ziehl Neelsen
- Phenol Auramine
Which mycobacteria are most likely to cause TB?
M. tuberculosis complex:
- M. bovis
- M. tuberculosis
What mycobacteria is most likely to cause leprosy?
M. leprae: hypopigmented lesions with anaesthesia
What atypical mycobacteria are most likely to be associated with HIV?
- M. avium complex
- M. kansasii
What mycobacteria is associated with fish tank granuloma?
M. marinum
Describe M. tuberculosis
- Co-infection with HIV
- Commonest infectious cause of adult death
- Global emergency
- Inhalation of infected resp droplets
- Usually pulmonary disease
Describe primary tuberculosis
- Periphery of lung midzone: most common site
- Inhaled bacilli phagocytosed by macrophages
- Hilar lymph nodes- Ghon focus
- Intracellular multiplication
- Dissemination via lymphatic system/ bloodstream
What is the body’s response to tubercle formation?
- Granuloma
- Cell mediated immune response
- Central area of epithelioid cells, giant cells
- Surrounding lymphocytic cell infiltration
- Central area caseous necrosis
- Fibrosis/calcification of lesions
- Bacilli slowly die
What are the clinical symptoms of TB and what tests need to be carried out?
- Influenza like syndrome
- chronic productive cough (haemoptysis)
- Weight loss
- Fever/ night sweats
- CXR (lung apices), cavitation
- Tuberculin skin test conversion
- Blood test: interferon-γ release assay
- Disseminated disease
What can cause TB to be reactivated?
- Lowered immunity- HIV
- Malnutrition
- Alcoholism
- Debilitating illness
- Silicosis
- Chronic renal failure
- Gastrectomy
- Anti TNFα blockade
What are the potential extra-pulmonary sites of TB?
- Pleura
- Lymph nodes
- Kidneys
- Bone
- Intestines
- Brain/ meninges
- Pericardium
- Epididymis
What is TB meningitis? How does it present?
- Often insidious onset
- Unidentified fever
- Personality change
- Focal neurological deficit (basilar inflammation)
- Mild headache/ meningism
- May lack constitutional quartet (fever, night sweats, anorexia, weight loss)
What is the standard treatment (for TB)?
2 mnths= isoniazid, rifampicin, pyrazinamide, ethambutol,(streptomycin)
4 mnths= rifampicin, isoniazid
-Meningitis/ pericarditis: 12mnth therapy initial treatment & w/ corticosteroids
-Other sites standard 6 mnth regime
What second line agents can be used for TB? Any new drugs for TB?
-Drug resistance
-Amikacin
-Ethionamide/ prothionamide
-Cycloserine
-Fluoroquinolones: ciprofloxacin, moxifloxacin
New drugs: Delamanid, Bedaloquine
