TB Flashcards
How is TB spread?
- Airborne
Where does mycobacterium invade and replicate?
- Aveolar macrophages
- Mycobacterium TB has thick, waxy mycolic acid capsule, protects it from toxic substances
Why is mycobacterium acid-fast?
- High mycolic acid in cell wall
What are granulomas?
- aggregates of epitheliod macrophages
- Multi-nucleated macrophages - Langhann giant cells
- Mycobacterium in granulomas can become dormant - latent TB
- Centre has caseous necrosis
How is a granuloma organised?
- Macrophages centrally, surrounded by a rim of lymphocytes
How can TB be killed?
- CD4 cells activate macrophages to kill bacilli
- CD8 release chemicals to break down affected cells
What stain is used for TB?
- Ziehl-Neelsen stain
What is primary TB?
- Usually in childhood
- Granuloma in mid zone of lung: GHON FOCUS
What is a primary complex?
- Ghon focus + hilar nodes
What is miliary TB?
- Dissemination of primary TB
What is secondary TB?
- Reactivation of latent TB (initial content may be years before)
What are key areas where latent TB occurs?
- Posterior subapical
- Upper part of lower lobes
What is a complication of secondary TB?
- Fibrotic cavities form
What factors are involved in reactivation of latent TB?
- HIV
- Immunosuppression
- Diabetes
- Aging
- Chronic illness
- Malnutrition
- Coal workers
How does acute tuberculosis bronchopneumonia arise?
- Arises from either primary or secondary TB
What is extra pulmonary TB? (EPTB)
- TB that occurs in organ systems other than the lungs
- GI tract, CNS, spinal cord, bone, lymph etc.
What is the pathology of extrapulmonary TB?
- Tissue destruction, fibrosis and scarring
- Granuloma, tuberculoma
- Cold abscess, exudates
What are classic examples of extrapulmonary TB?
- CNS: TB meningitis in developing nations
- Lymph: neck
- Bone: spine
- TB arthritis: spine, destruction of vertebrae
What are non-tuberculosis mycobacteria?
- Mycobacterium avium-intracellulare
- Mycobacterium kansasii
- Mycobacterium marinum
How is TB acquired?
latent or active?
- From person with ACTIVE TB infection
What is the most common TB?
- Latent, 90%
How often does latent TB become active TB?
- 5-10% of times
What are symptoms of pulmonary TB?
- Drenching night sweats
- Weight loss
- Fever
- Productuve cough
- Haemoptysis
What are the symptoms of extra-pulmonary TB?
TB lymphadenitis: swollen lymph nodes
TB osteomyelitis: pain at site of infection
TB meningitis: drowsy, headache, neck stiffness
What are signs of TB?
- Cachexia
- Clubbing (pulmonary TB)
- Coarse crackles (pulmonary TB)
- Palpable lymph, tenderness, confusion (extra-pulmonary TB)
How is latent TB tested?
- Tuberculin test (Mantoux)
- Quantiferon test
How is active TB tested?
- Culture
- Ziehl-Neelsen
How is PCR used to test for TB?
- TB geneXpert
- definitive diagnosis made in 2 hrs
- testd for Rifampicin resistance
How is extra-pulmonary TB diagnosed?
- Biopsy from specific region
How is latent TB managed?
- Rifampicin 4 months
- Isoniazid 9 months
not mandatory to take for latent
How is active TB managed?
- RIPE
- multiple drugs used to reduce risk of drug resistance
- 6 months to 2 years
What infection does TB co-exist with?
- HIV
