Lecture 14 - Mycobacteria

Lecture 14 - Mycobacteria - Lecture 14 - Mycobacteria...

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Lecture 14 - Mycobacteria MI-32a. Describe the staining characteristics used to visualize mycobacteria in the laboratory Runyon Classificaiton of Mycobacteria Pigment production, rate of growth on solid agar Runyon group I: slow growing photochromogens ; pigment after exposure to light Runyon group II: slow growing scotochromogens ; pigment produced in the dark Runyon group III: slow growing nonchromogens ; no pigment Runyon group IV: rapid growers Phylogeny Classification of Mycobacteria - sequencing phylogenetic trees (based on 16s rRNA sequences) - DRAW! Mycobacterium tuberculosis Intracellular pathogen (macrophages cell line); human reservoir Aerobic , non-spore-forming, non-motile 4µm bacillus Grows slowly (3-8 wks) on agar media (L-J agar, 7H10 agar or liquid media); buff-colored, rough, friable colonies Pink/Fuasia staining ( acid-fast ) with Ziehl-Neelson ; orange-yellow fluorescence with auramine- rhodamine Identified biochemically (acid-fast, niacin production, nitrate reduction, inactivation of catalase at 68 o C), mycolic acid HPLC, or by nucleic acid probe MI-32b. Identify the immune responses that protect against infections with mycobacteria MI-32c. Describe the growth properties, virulence factors and pathogenesis of Mycobacterium tuberculosis TB Pathogenesis Droplet inhalation and deposition (airborne through sputum) Pulmonary macrophage ingestion (after deposit in new airway); spread to regional lymph nodes followed by lymphohematogenous dissemination (replicating the bacteria before the immune response to escape to other organs) Cell-mediated immune response 6-12 weeks (if never exposed) T-helper lymphocytes And trigger migration Granuloma formation (tissue response) Recruitment of macrophages (surround organism and contain it) Bacterial lysis, infection arrest, calcification, involution à normal process for someone who does not develop disease Pneumonitis, caseation necrosis, tissue destruction, fibrosis à progression of pathologic response Primary progression or resolution/quiescence Progression to spread to cause more disease (primary progressive pneuomonia) The majority will go to the calcification and remain lament MI-32d. Describe the epidemiology, transmission and clinical manifestations of infection with M. tuberculosis in both its pulmonary and extrapulmonary forms Risk of developing active TB This infection is host dependent After index exposure - ~30% become ‘infected’ Depending on the time and duration of exposures (high likelihood with high risk if exposed longer) Non-immunocompromised host: 5% risk of developing active TB within 2 years; ~5%-10% life time risk thereafter Reactivation TB rate TST (+) = 12.9 per 1,000 person- years HIV-infected and other immunosuppressed hosts: ~30% risk of developing active TB within 1 year after index exposure Reactivation TB rate if TST (+) = 35-162 per 1,000
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This note was uploaded on 09/14/2011 for the course PHARM mb taught by Professor Staff during the Spring '11 term at UCSD.

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Lecture 14 - Mycobacteria - Lecture 14 - Mycobacteria...

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