Pathogenic anaerobe gram positive bls 209

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Pathogenic anaerobe gram positive bls 209

  1. 1. Corynebacterium Erysipelothrix & Listeria
  2. 2. Pathogenic Anaerobic Gram-Positive Bacilli
  3. 3. 1. Corynebacteria (Genus Corynebacterium )  Aerobic or facultatively anaerobic  Small, pleomorphic (club-shaped), gram-positive bacilli that appear in short chains (“V” or “Y” configurations) or in clumps resembling “Chinese letters”  Cells contain metachromatic granules (visualize with methylene blue stain)  Lipid-rich cell wall contains meso-diaminopimelic acid, arabino-galactan polymers, and short-chain mycolic acids  Lysogenic bacteriophage encodes for potent exotoxin in virulent strains
  4. 4. Distinguishing Features of CMN Group Corynebacterium Mycobacterium Nocardia    
  5. 5. Pathogenic Corynebacterial Species <ul><ul><li>Corynebacterium diphtheriae </li></ul></ul><ul><ul><li>Corynebacterium jeikeium </li></ul></ul><ul><ul><li>Corynebacterium urealyticum </li></ul></ul>
  6. 6. <ul><li>Corynebacterium urealyticum </li></ul><ul><ul><li> Urinary tract infections (UTI’s); rare but important </li></ul></ul><ul><ul><li> Urease hydrolyzes urea; release of NH 4 + , increase in pH, alkaline urine, renal stones </li></ul></ul>
  7. 7. <ul><li>Corynebacterium diphtheriae </li></ul><ul><ul><li> Respiratory diphtheria (pseudomembrane on pharynx) and cutaneous diphtheria </li></ul></ul><ul><ul><li> Prototype A-B exotoxin acts systemically </li></ul></ul><ul><ul><ul><li>Toxoid in DPT and TD vaccines </li></ul></ul></ul><ul><ul><li> Diphtheria toxin encoded by tox gene introduced by lysogenic bacteriophage (prophage) </li></ul></ul><ul><ul><li> Selective media: cysteine-tellurite; serum tellurite; Loeffler’s </li></ul></ul><ul><ul><li> Gravis, intermedius, and mitis colonial morphology </li></ul></ul>
  8. 8. Epidemiology of Diphtheria
  9. 9. Virulence Factors in Corynebacterium Species
  10. 10. Diphtheria tox Gene in Beta Bacteriophage and Prophage
  11. 11. See Handout on Exotoxins
  12. 13. Mechanism of Action of Diphtheria Toxin: Inhibition of Protein Synthesis
  13. 14. Molecular Structure of Diphtheria Toxin Catalytic Region Receptor-Binding Region Translocation Region A Subunit B Subunit
  14. 15. Heparin-binding epidermal growth factor on heart & nerve surfaces
  15. 16. Diagnostic Schick Skin Test TOXIN TOXOID Immune Status to C. diphtheriae and Sensitivity to Diphtheria Toxoid
  16. 17. In vivo Detection of Diphtheria Exotoxin
  17. 18. 2. Genus Listeria
  18. 19. 2.Listeria monocytogenes <ul><li>Small, Gram +, nonsporing rod </li></ul><ul><li>End-over-end tumbling motility when grown at 20-25°C, not at 37°C </li></ul><ul><li>Facultative anaerobe, ß-hemolytic </li></ul><ul><li>CAMP Test positive (like Group B Streptococcus ) </li></ul>
  19. 20. Listeriosis <ul><li>Humans, domestic animals </li></ul><ul><ul><li>described in ≥ 40 species of animals </li></ul></ul><ul><ul><li>usually follows ingestion </li></ul></ul><ul><ul><li>outbreaks, sporadic cases related to food </li></ul></ul><ul><ul><li>asymptomatic fecal carriage common, especially for those in contact with domestic animals </li></ul></ul><ul><ul><li>Incidence increases in summer, when outbreaks of food-borne disease are more common. </li></ul></ul>
  20. 21. <ul><ul><li>Neonates, elderly & immunocompromised </li></ul></ul><ul><ul><li>Granulomatosis infantiseptica </li></ul></ul><ul><ul><ul><li>Transmitted to fetus transplacentally </li></ul></ul></ul><ul><ul><ul><li>Early septicemic form: 1-5 days post-partum </li></ul></ul></ul><ul><ul><ul><li>Delayed meningitic form: 10-20 days following birth </li></ul></ul></ul><ul><ul><li>Intracellular pathogen </li></ul></ul><ul><ul><ul><li>Cell-mediated and humoral immunity develop </li></ul></ul></ul><ul><ul><ul><li>Only cell-mediated immunity is protective </li></ul></ul></ul>Listeriosis
  21. 22. <ul><ul><li>Intestinal tract of mammals & birds (especially chickens) </li></ul></ul><ul><ul><li>Persists in soil </li></ul></ul><ul><ul><li>Soft cheeses & unwashed raw vegetables </li></ul></ul><ul><ul><li>Raw or undercooked food of animal origin </li></ul></ul><ul><ul><ul><li>Luncheon meats </li></ul></ul></ul><ul><ul><ul><li>Hot dogs </li></ul></ul></ul><ul><ul><li>Large scale food recalls have become common </li></ul></ul>Distribution of Listeria?
  22. 23. Epidemiology of Listeria Infections Natural Reservoirs Common Routes for Human Exposure Population at Greatest Risk
  23. 24. Virulence Factors and Pathogenesis - Motility <ul><li>Actin-mediated motility (ActA) </li></ul><ul><ul><li>host cell actin polymerized </li></ul></ul><ul><ul><li>growth of tail by actin polymerization at end of bacterium propels it through cytoplasm </li></ul></ul><ul><li>Uptake: induced phagocytosis </li></ul><ul><ul><li>internalin </li></ul></ul><ul><ul><li>similar to M protein of S. pyogenes (antiphagocytic), dissimilar functions </li></ul></ul>
  24. 25. Virulence Factors and Pathogenesis <ul><li>After entry to epithelial cells </li></ul><ul><ul><li>escapes phagosome, multiplies in cytoplasm </li></ul></ul><ul><ul><li>exocytosis from epithelial cell followed by phagocytosis by MØ, PMN </li></ul></ul><ul><ul><li>multiplication followed by death of phagocytes, secondary phagocytosis </li></ul></ul><ul><ul><li>systemic spread </li></ul></ul>
  25. 26. Virulence Factors and Pathogenesis - Listeriolysin <ul><li>Major virulence factor: listeriolysin </li></ul><ul><ul><li>thiol-activated cytolysin, hemolysin </li></ul></ul><ul><ul><li>mediates escape from phagocytic vesicle </li></ul></ul><ul><li>LLO mutants: LD 50 5 logs higher than WT, do not survive in MØ </li></ul>
  26. 27. Virulence Factors and Pathogenesis <ul><li>Bacteria encountering plasma membrane continue to move forward </li></ul><ul><ul><li>produce protrusions extending into adjacent cell: listeriopods </li></ul></ul><ul><ul><li>escape listeriopod in double-membrane vesicle, enter cytoplasm of adjacent cell </li></ul></ul><ul><li>Mediated by phospholipase </li></ul>
  27. 28. Virulence Factors and Pathogenesis - Actin-based Motility <ul><li>Bacteria in cytoplasm polymerize actin, form tails </li></ul><ul><ul><li>hollow mesh forms on surface, left behind as bacterium moves forward </li></ul></ul><ul><ul><li>invade adjacent cells </li></ul></ul><ul><li>Actin nucleating factor: ActA </li></ul><ul><ul><li>ActA localized at one end of the bacterium, not found in tail </li></ul></ul>
  28. 30. Intracellular Survival & Replication of Listeria Listeriolysin O? Macrophage Macrophage Phagocytosis Intracellular Replication Actin Filaments
  29. 31. Immune Response <ul><li>In infected mice, bacteria first appear in MØ, then invade hepatocytes </li></ul><ul><ul><li>most replication probably occurs in liver </li></ul></ul><ul><ul><li>infection of MØ leads to presentation of antigens with MHC class I, stimulating cytotoxic T cell response </li></ul></ul><ul><ul><li>cytotoxic T cells (and NK cells) kill infected hepatocytes </li></ul></ul>
  30. 32. <ul><ul><li>bacteria released from lysed host cells killed bv activated MØ </li></ul></ul><ul><ul><li>T cell-deficient mice survive infection: cytotoxic T-cell response helps clear hepatocytes, not essential </li></ul></ul><ul><ul><li>increased susceptibility in mice unable to produce IFN-  suggests importance of activated MØ </li></ul></ul>
  31. 33. Erysipelothrix rhusopathiae <ul><li>Gram-positive non-motile bacillus; forms filaments </li></ul><ul><li>Occupational disease of meat and fish handlers, hunters, veterinarians </li></ul><ul><ul><li>Preventable with protective gloves & clothing </li></ul></ul><ul><li>Erysipeloid in humans; erysipelas in swine & turkeys </li></ul><ul><ul><li>Organisms enter through break in skin </li></ul></ul><ul><ul><li>Nonsuppurative, self-limiting skin lesions with erythema and eruption </li></ul></ul><ul><ul><li>Peripheral spread may lead to generalized infection, septicemia and/or endocarditis </li></ul></ul><ul><ul><li>Organisms can be isolated from skin biopsy </li></ul></ul>
  32. 34. Epidemiology of Listeriosis
  33. 35. Epidemiology of Listeria Infections Natural Reservoirs Common Routes for Human Exposure Population at Greatest Risk
  34. 36. <ul><ul><li>Neonates, elderly & immunocompromised </li></ul></ul><ul><ul><li>Granulomatosis infantiseptica </li></ul></ul><ul><ul><ul><li>Transmitted to fetus transplacentally </li></ul></ul></ul><ul><ul><ul><li>Early septicemic form: 1-5 days post-partum </li></ul></ul></ul><ul><ul><ul><li>Delayed meningitic form: 10-20 days following birth </li></ul></ul></ul><ul><ul><li>Intracellular pathogen </li></ul></ul><ul><ul><ul><li>Cell-mediated and humoral immunity develop </li></ul></ul></ul><ul><ul><ul><li>Only cell-mediated immunity is protective </li></ul></ul></ul>Listeriosis
  35. 37. Methods That Circumvent Phagocytic Killing See Chpt. 19
  36. 38. Intracellular Survival & Replication of Listeria Listeriolysin O? Macrophage Macrophage Phagocytosis Intracellular Replication Actin Filaments
  37. 39. 3. Erysipelothrix rhusopathiae <ul><li>Gram-positive non-motile bacillus; forms filaments </li></ul><ul><li>Occupational disease of meat and fish handlers, hunters, veterinarians </li></ul><ul><ul><li>Preventable with protective gloves & clothing </li></ul></ul><ul><li>Erysipeloid in humans; erysipelas in swine & turkeys </li></ul><ul><ul><li>Organisms enter through break in skin </li></ul></ul><ul><ul><li>Nonsuppurative, self-limiting skin lesions with erythema and eruption </li></ul></ul><ul><ul><li>Peripheral spread may lead to generalized infection, septicemia and/or endocarditis </li></ul></ul><ul><ul><li>Organisms can be isolated from skin biopsy </li></ul></ul>
  38. 40. Epidemiology of Erysipelothrix Infection

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