Tuberculosis
- Created by: L1ttl3N1amh
- Created on: 27-12-17 13:23
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- Tuberculosis
- Mycobacterium
- Tuberculosis
- Bovis
- Africanum
- Structure
- aerobic
- non-motile
- outer membrane and capsule present
- slow growing - 20 hours generation time
- waxy coating = resistant to environmental stress, antibiotics and disinfectants
- transmitted via aerosol droplets
- Can survive in the environment for several hours
- spread best in dark, humid conditions
- Factors affecting transmission
- poor health care
- overcrowding
- individual behaviour
- immigration
- occupation
- HIV positive status
- Prevention
- prophylaxis with isoniazid
- Identify infectious cases
- Diagnosis
- Staining with zeihl-neilson
- Acid fast
- Heaf skin test
- X-ray of lung
- only detects previous exposure not active disease
- culture on Lowenstein-Jensen Media
- Automated culture
- grow in liquid media, monitored by computer
- Automated culture
- PCR
- quick but expensive
- can diagnose resistant strains
- quick but expensive
- Fluorescent microscopy
- Staining with zeihl-neilson
- Pathogenesis
- Step 1
- TB inhaled, engulfed by alveolar macrophages in healthy people
- avoid entrapment by cilia and mucus
- Step 2
- immunocompromised patients
- bacteria spread before host response activated
- transported to local hilar lymph nodes
- cell mediated response
- may infect bloodstream and travel to other organs
- Disseminated disease
- Step 3
- influx of immune cells
- tubercules form in lungs
- giant cells and epitheloid tissue
- primary complex
- enlarged lymph node and lung lesion
- Step 4
- bacteria remain inside lesion after healing
- bacteria lie dormant and protected
- change in immune status = reactivation
- Step 5
- Cavity formation
- bacteria grow and multiply
- cellular stress
- enzymes leak from lysozymes causing breakdown of tissue
- caseous necrosis due to liquefaction of lesion
- Step 1
- Treatment
- slow as antibiotics work on growing bacteria
- macrophages prevent antibiotics reaching bacteria
- Two stage treatment
- Initial
- 1-2 months
- controls infection
- prevents development of resistance
- continuation
- 4-7 months
- kill bacteria in lesions
- Initial
- anti-TB drugs
- izoniazid
- kills dividing bacteria
- rifampicin
- ethambutol
- streptomycin
- izoniazid
- don't finish/misuse prescription, wrong dose/length of time
- Drug resistant TB
- MDR-TB
- resistant to isoniazid and rifampicin
- primary infection with resistant bacteria
- may develop through course of treatment
- treatment more expensive, longer and uses more toxic drugs
- XDR-TB
- resistant to rifampicin, isoniazid and fluorquinolones
- risk to HIV+ and immunocompromised
- higher risk of death
- 2 year treatment with more toxic drugs
- rare but reported in 117 countries
- resistance mechanisms
- spontaneous mutation
- transfer of resistance mechanisms
- alteration of target site
- inactivation of drug using conjugation, hydrolysis or redox
- efflux pumps
- varying outer membrane permeability
- MDR-TB
- Mycobacterium
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