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MYCOBACTERIA CORYNEBACTERIA Lecture 40

MYCOBACTERIA CORYNEBACTERIA Lecture 40. Faculty: Dr. Alvin Fox. Acid Fast Tuberculosis (TB) M. tuberculosis (MDR, XDR) M. avium - M. intracellulare complex M. bovis M. leprae Tubercle PPD Tuberculin Mycobactin Cord factor BCG Leprosy (Hansen's Disease) AIDS and TB

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MYCOBACTERIA CORYNEBACTERIA Lecture 40

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  1. MYCOBACTERIACORYNEBACTERIALecture 40 Faculty: Dr. Alvin Fox

  2. Acid Fast Tuberculosis (TB) M. tuberculosis (MDR, XDR) M. avium - M. intracellulare complex M. bovis M. leprae Tubercle PPD Tuberculin Mycobactin Cord factor BCG Leprosy (Hansen's Disease) AIDS and TB Runyon groups Mycolic acids Diphtheria C. diphtheriae Loeffler's agar Tellurite agar Metachromatic bodies Diphtheria toxin Schick test Diphtheroids KEYWORDS

  3. Mycobacterium tuberculosis obligate aerobe acid-fast rods

  4. Tuberculosis (TB, consumption) • M. tuberculosis • major human disease • healthy people • problems • association with AIDS • multiple drug-resistance

  5. M. avium- M. intracellulare complex (M. avium) • non-AIDS • infection almost never • AIDS • major bacterial opportunist • multiple drug-resistance

  6. M. bovis • spread from cattle • infected cattle are culled • positive skin test • rarely seen in US

  7. M. leprae • leprosy • major disease of third world • rare in US

  8. Transmission -tuberculosis • M. tuberculosis causes disease • healthy individuals • transmitted man-man • airborne droplets

  9. Pathogenesis of tuberculosis • infects lung • distributed within macrophages • facultative intracellular pathogen • inhibits phagosome-lysosome fusion

  10. Cell-mediated immunity -tuberculosis • infiltration • macrophages • lymphocytes • granulomas • tubercules

  11. Laboratory diagnosis - tuberculosis • skin testing • delayed hypersensitivity • tuberculin • protein purified derivative, PPD • X-ray

  12. Positive skin test -tuberculosis • indicates exposure to organism • does not indicate active disease

  13. Other minor pathogenesis factors • tuberculosis • mycobactin • siderophore • cord factor • damages mitochondria

  14. Laboratory diagnosis M. tuberculosis • acid fast bacteria • sputum

  15. Laboratory diagnosis M. tuberculosis (culture) • grows very slowly • two weeks or longer • non-pigmented colonies • niacin production • differentiates from other mycobacteria

  16. Tuberculosis • polymerase chain amplification • rapid diagnosis

  17. Antibotic treatment - tuberculosis • extensive time periods (e.g. 9 months) • organism grows slowly, or dormant • two or more antibiotics • e.g. rifampin and isoniazid • resistance minimized

  18. Tuberculosis and Drug resistance • Multiple drug resistant (MDR) • resistant to first line drugs • Extremely drug resistant (XDR) • Resistant to some of the second line drugs • Nearly un-treatable

  19. Vaccination • BCG vaccine • an attenuated strain of M. bovis • not effective • in US, • incidence is low • vaccination not practiced • immunization interferes with diagnosis

  20. Mycobacterium leprae

  21. Leprosy (Hansen's Disease) • M. leprae • causative agent • chronic disease • disfigurement • rarely seen in the U.S. • common in third world - effective antibiotic therapy recently initiated, incidence way down • infects the skin • low temperature

  22. ulcers, resorption of bone • worsened from careless use of hands (nerve damage)

  23. Leprosy • tuberculoid • few organisms • active cell-mediated immunity • lepromatous • many organisms • immunosuppression

  24. Production of M. leprae antigens and pathogenesis studies • in vitro • unculturable • in vivo growth • low temperature • armadillo (laboratory and native [e.g. TX]) • mouse footpad

  25. Leprosy • lepromin • skin testing • acid-fast stains • skin biopsies • clinical picture

  26. Other mycobacterial species (including M. avium) • infect immunocompromised host • not transmitted man-man, healthy people • M. avium – common • Other species - rare

  27. Mycobacterial diseases • tuberculosis-like • leprosy-like

  28. Mycobacteria and AIDS • M. aviumis much less virulent than M. tuberculosis • does not infect healthy people • infects AIDS patients • M. avium infects • when CD4 (helper T cell) count greatly decreased • M. tuberculosis infection • infects healthy people • infects AIDS patients • earlier stage of disease • more systemic

  29. Clinical features with AIDS • systemic disease (versus pulmonary) • greater in AIDS • lesions often lepromatous

  30. Antibiotic therapy • selected primarily for M. tuberculosis • if M. avium involved other antibiotics included

  31. Other species • pigmented or not • pigmentation • in the light • in the dark • growth • fast • slow

  32. Mycobacterial species identification • cellular fatty acid profiles • mycolic acid profiles • genetic markers

  33. Mycolic acids • mycobacteria • longest chain length • strongly acid fast • nocardia • intermediate chain length • weakly acid fast • corynebacteria • shortest chain length • not acid fast

  34. Corynebacterium diphtheriae Gram positive strict aerobe pleomorphic (e.g. club-shaped)

  35. Diphtheria • member of normal flora of pharynx • overgrowth upper respiratory tract • pseudomembrane • chocking • bacteria do not spread systemically • The toxin does disseminates • .

  36. This child has diphtheria resulting in a thick gray coating over back of throat. This coating can eventually expand down through airway and, if not treated, the child could die from suffocation CDC

  37. Diptheria toxin • spreads • systemic and fatal injury

  38. Diphtheria toxin • B binds to host cell • A inhibits protein synthesis • ADP-ribose moiety (NADH) attaches • elongation factor 2 inhibited

  39. Treatment • anti-toxin • antibiotic

  40. Immunization against diphtheria (infant) • diseasevanished in US • without immunization will return • toxoid (+ pertussis and tetanus) DPT • neutralizing antibodies • colonization not inhibited • found in normal flora

  41. Testing immunity • Schick skin test • toxin

  42. Diphtheria toxin • coded by bacteriophage tox gene • not synthesized if iron present • iron-repressor complex forms • inhibits expression of tox gene

  43. Identification - C. diphtheriae • growth Loeffler's medium • stain for polyphosphate granules • metachromatic • polyphosphate granules (pink) cell (blue) • tellurite agar • reduction by bacteria • tellurium precipitation • black colonies

  44. Identification – Exotoxin production • in vivo • in vitro

  45. C. diphtheriae should not be confusedwith: • diphtheroids • other corynebacteria • propionibacteria

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