Mycobacteria Lecture Notes PDF

Mycobacteria  Mycobacteria Causative agents of tuberculosis and leprosy Waxy coat NO Gram stain Resistant to disinfectants Acid-fast bacilli Resist decolorisation Use Ziehl-Neelsen staining technique 1. Ziehl-Nee...

Mycobacteria  Mycobacteria Causative agents of tuberculosis and leprosy Waxy coat NO Gram stain Resistant to disinfectants Acid-fast bacilli Resist decolorisation Use Ziehl-Neelsen staining technique 1. Ziehl-Neelsen carbol fuchsin to the slide for five minutes while applying heat. 2. Follow with a gentle wash with water to cool the slide. 3. Acid alcohol is now added to decolorize the slide. 4. Wash the slide in water again and counterstain with methylene blue for 1-2 minutes.  Mycobacterium tuberculosis Chronic slow-progressing pulmonary infection; transmission by aerosol droplets Obligate aerobe, facultative intracellular parasite 4-6 WEEKS to see colonies on a plate Lowenstein-Jensen medium Use microscopy of sputum smears as first line of diagnosis Leading cause of death world-wide form a M.tuberculosis colonies single infection (Bacteriology, Kenneth Todar, 2005) Affects 1.7billion/year Declining in US Infection develops in stages  Primary Tuberculosis Aerosol inhalation Bacteria multiplication in alveoli Macrophage ingestion of bacilli and formation of 1º complex Foci of infection in lungs (may be spread to kidneys, bones, meninges) ~ 6 weeks CMI is fully active, infection is stopped (majority of cases) Some bacilli survive, reactivation several years later Positive tuberculin test  Mycobacterium tuberculosis Post-primary tuberculosis Late reactivation of lesions in lungs, kidneys, bones etc 5% of cases; higher in patients with AIDS Chronic infection  Immunity in Tuberculosis Cell mediated immunity is most important (T-cells) Mantoux test Tuberculin solution is injected INTRADERMALLY, wait 48-72 hrs, check for induration Record diameter of induration >10mm POSITIVE 5-9 mm Doubtful, maybe cross reaction with other Mycobacteria