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Mycobacterium

Mycobacterium. Filename: Myco.ppt. Outline. Microbial characteristics Diseases Tuberculosis Leprosy Treatment Prevention. Mycobacterium. Mycobacteriaceae are represented by the single genus Mycobacterium Closely related to the genera Corynebacterium and Nocardia. Rhodococcus

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Mycobacterium

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  1. Mycobacterium Filename:Myco.ppt

  2. Outline • Microbial characteristics • Diseases • Tuberculosis • Leprosy • Treatment • Prevention

  3. Mycobacterium • Mycobacteriaceae are represented by the single genus Mycobacterium • Closely related to the genera Corynebacterium and Nocardia.Rhodococcus • previously called the CNM group

  4. CELLULAR Morphology • Strongly acid fast weakly Gram positive • Form rods with occasionally branched filaments and no aerial mycelium. • Non motile, no spores, no capsule

  5. COLONIAL Morphology • Solid surface • The time for visible colonies 2-40 days • Diffusable pigments are rare

  6. Saprophytic Mycobacteria • Grow at 22 C • Grow rapidly • Produce pigment • weakly acid fast Easily confused with pathogens

  7. Growth ParametersMycobacterium • PHYSIOLOGICAL • aerobes • resistant to penicillin • divided into two groups • generally grow slowly • some grow fast • high lipid content in both the cell and the cell wall

  8. Growth Media • Simple synthetic media * • Complex Organic media ** • Oleic acid Albumin ***

  9. Simple synthetic media • growth poor • large inocula • slow • toxic fatty acids inhibit growth • Fatty acids neutralized by serum or albumin • activated charcoal helps

  10. Oleic Acid Albumin Medium • Hydrophobic cell wall • Mycobacteria grow in clumps • Tweens wet surface of cells • Disperse clumps • Encourage more rapid growth

  11. Mycobacterial Cell Wall • “Cord Factor” • virulence • Protein Fraction • tuberculin test • Lipids • Acid fast • symptoms • Polysaccharides • immunity?

  12. Cord factor • Serpentine cords • found in cell wall • mycolic acid • trehalose- 6,6’ dimycolate • inhibits leucocytes • chronic granulomas

  13. Cell Wall

  14. Adjuvanticity • Muramyl dipeptide • subunit of peptidoglycan • Stimulates immune response non-specifically

  15. Protein fractions • In cell wall • bound to waxes • tuberculin sensitivity !!! • induce antibodies???

  16. Mycobacterial Lipids • Cell wall rich in lipids • Responsible for acid fast reaction • Induce adverse cellular immunity • Caseation necrosis

  17. Tuberculin Test: Method • Injected subdermally with protein extract • OT Old tuberculin • PPD Purified Protein Derivative

  18. Tuberculin Reaction • develops 24-48 hours • read after 48-72 hours • edema, erythema • necrosis • >10 mm

  19. Tuberculin Test:Interpretation • Positive • infected with tuberculosis in past • risk of developing the disease • confirm with X rays • antibiotic therapy • Negative • never infected • high risk occupations • immunize?

  20. Mycobacterium:Diseases • Chronic long term diseases • Tuberculosis • Mycobacterium tuberculosis • Koch 1982 • Other mycobacteria produce similar disease • M. bovis, M. avium, M kansasii, M. intracellular • Leprosy • Mycobacterium leprae • Hansen 1873

  21. Other Mycobacterial Diseases • Skin infections • Mycobacterium tuberculosis • Mycobacterium marinum • Mycobacterium ulcerans • Lymph glands • Mycobacterium scrofulaceum • Mycobacterium tuberculosis

  22. Localized Infection Entry Respiratory Disease Pneumonia granulomatous lesions Exit respiratory Systemic Infection Entry respiratory Spread Lymphatic & hematogenous Disease granulomas any site Exit respiratory Tuberculosis

  23. Tuberculosis • Two types • Primary -Exudative tuberculosis • Reactivation-Productive tuberculosis • Initial sites • lungs, gastrointestinal tract • Spread through lymphatics to lymph nodes • intracellular!!! • later spread through blood stream • Secondary sites • ALL organs except muscle

  24. Radiologic Differences between primary and post primary tuberculosis

  25. X-Ray primary TB

  26. Exudative tuberculosis • Acute inflammatory reaction • Tuberculin positive • Frequent in lungs • Pneumonia symptoms • edema fluid • PMNs around the bacteria • Later monocytes • Outcomes • heal • tissue necrosis • Productive TB

  27. Productive Tuberculosis • Secondary spread • Chronic granuloma • Centre multinucleated giant cells • Midzone of epitheloid cells • Periphery- fibroblasts monocytes • Tubercle • granuloma becomes fibrous • caseation necrosis • calcification

  28. Treatment • Antituberculosis drugs • Isoniazid • Ethambutol • Rifampin • Streptomycin • Multiple drug resistant strains • Thus drugs used concomitantly • Strept + INH; INH + ethambutol; ethamubutol +rifampin etc

  29. Prevention & Control • Public health measures • Tuberculin X rays • Eradicate bovine tuberculosis • slaughter • pasteurization • treat asymptomatic converters in children • Immunization • BCG - inadequate • high risk groups nurses, lab techs, vets

  30. The End

  31. Short Answers • Construct a table of the virulence factors associated with ??? and the biological activity of each • Describe the clinical manifestations of ??? • Construct a table listing the common ??? species and the associated human diseases.

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