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.
What are the benefits of using NAAT for TB?
Rapid diagnosis and may show drug resistant mutations, allowing careful planning to avoid them.
What is the tuberculin sensitivity test (TST)?
What are the limitations?
Intradermal injection of tuberculin causing skin hypersensitivity reaction in those with previous mycobacterium infection. Diameter of swelling is measured 48-72 hours later.
Limitations - cannot differentiate causes of TB from other mycobacterium and BCG vaccination. False negatives in immune suppressed.
What is the benefit of interferon gamma testing for latent TB?
It does not cross react with the BCG vaccine.
What first line medications are given for TB?
Rifampicin,
Isoniazid,
Pyrazinamide,
Ethambutol.
What secondary medications may be considered for TB?
Quinolones (moxifloxacin),
Cycloserine,
Linezolid,
Colfazamine.
What is the treatment regime used for TB?
3 or 4 drugs used for 2 months, followed by Rifampacin and Isoniazid for 4 months. Vitamin D supplementary provided.
What methods may be used to test adherence to TB medication?
Directly observed therapy or video observed therapy.
How is multi drug resistant TB classified?
How is extremely drug resistant TB classified?
Resistance to rifampicin and isoniazid (XDR also fluoroquinolones and at least 1 injectable)
How are drug resistant TB strains treated?
After suspicions confirmed with positive culture after 5 months, 4 to 5 drug regime for longer duration with quinolones, aminoglycosides,PAS cycoserine and ethionamide.
What is Miliary TB?
Bacilli spread through bloodstream. Always affects the lungs resulting in miliary nodulation.
What is the name given to Spinal tuberculosis infection?
Potts disease
What extra measures are taken in the prevention of spread of TB?
Contact tracing procedures, negative pressure isolation of patients, vaccination (BCG to M bovis).
