TB Flashcards
Who is most at risk of TB?
HIV and immunosuppressed, Homeless, Prisoners, Drug users, Recent migrants or non UK born. More prevalent in young adults.
What are the three most common mycobacterium species that cause TB?
M tuberculosis, M bovis, M africanum.
What type of bacterium is mycobacterium tuberculosis?
Non motile bacillus and an obligate aerobe.
Why is the gram stain not used for mycobacterium?
What staining is used instead?
Mycolic acid and glycolipid cell wall resistant to staining.
Acid alcohol fast stains used (ZN or Auramine).
How long might it take to catch TB from another person?
Requires prolonged exposure eg 8 hours per day for up to 6 months.
What is the pathogenesis of TB?
- Mycobacterium aerosols Inhaled 2.engulfed by macrophages 3.transferred by macrophage to local lymph nodes 4. Formation of primary complex (gohns focus) 5. Infection progresses to tuberculosis in 5% or goes latent 6. Infection recurs in 5% with latent infection.
What are common risk factors for TB reactivation and post primary TB?
Infection with HIV, Organ transplants, Severe kidney disease, Diabetes mellitus, Low body weight.
How is latent TB infection confirmed?
TST or interferon gamma testing positive.
What are common sites of TB?
Lungs (pulmonary).
Extrapulmonary - Larynx, lymph nodes, pleura, brain, kidneys, bones and joints.
Systemic - Miliary TB.
What is indicative of TB on histology?
Caseating granulomata and langhans giant cells.
What are the symptoms of pulmonary TB?
Cough, Fever, Weight loss, Night sweats, Fatigue, Haemoptysis.
What CXR abnormality indicates TB?
Miliary nodulation. Also cavitation and fibrosis.
How is TB diagnosed?
Sputum culture. Can be collected with broncho-alveolar lavage.
Which part of the lungs is commonly affected by TB?
Apex - I’ll defined patchy consolidation with cavitation.
What does a positive smear case for TB indicate?
The patient is likely infectious.
