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pathogenesis

pathogenesis. KOCH’S POSTULATES. Diseased animal. Healthy animal. The Postulates:. Tools:. 1. The suspected pathogenic organism should be present in all cases of the disease and absent from healthy animals. Microscopy, staining. Red blood cell. Observe

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pathogenesis

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  1. pathogenesis

  2. KOCH’S POSTULATES Diseased animal Healthy animal The Postulates: Tools: 1. The suspected pathogenic organism should be present in all cases of the disease and absent from healthy animals. Microscopy, staining Red blood cell Observe blood/tissue under the microscope Red blood cell Suspected pathogen Fig. 1-15 2. The suspected organism should be grown in pure culture. Laboratory culture Streak agar plate with sample from either diseased or healthy animal No organisms present Colonies of suspected pathogen Inoculate healthy animal with cells of suspected pathogen 3. Cells from a pure culture of the suspected organism should cause disease in a healthy animal. Experimental animal Diseased animal Remove blood or tissue sample and observe by microscopy Pure culture (must be same organism as before) Suspected pathogen 4. The organism should be reisolated and shown to be the same as the original. Laboratory reisolation Laboratory culture

  3. Primary pathogens: Cause disease in healthy hosts Opportunisitc pathogens: Cause disease only in immunocompromised patients Virulence is a measure of the severity of a disease. - Infectious dose vs. lethal dose Figure 25.5

  4. Figure 25.6

  5. Figure 25.11 Figure 25.13A

  6. Table 28-3

  7. Streptococcus pyogenesM protein Bordetella pertussis Pertactin Figure 25.14 Figure 25.14 Bacteria can attach to surfaces in bulk, forming a biofilm. - Play important roles in chronic infections Figure 25.15A

  8. Figure 25.16

  9. AB Toxins B subunit: Binds to host cell - Delivers A subunit to cytoplasm - Often five B subunits form a pore for A entry. Figure 25.17A A subunit: Has toxic activity - ADP-ribosyltransferase - Diphtheria toxin - Cholera toxin Figure 25.17B

  10. Figure 13.7A

  11. Figure 25.20

  12. Animation: Cholera Toxin Mode of Action ADP-Ribosylating Toxins Click box to launch animation

  13. Alpha Toxin The hemolytic alpha toxin is produced by Staphylococcus aureus. - Forms a transmembrane, seven-member pore in target cell membranes Figure 25.18

  14. Anthrax Toxin Made by Bacillus anthracis Two active toxins: - Edema factor raises cAMP levels. - Causes fluid secretion, tissue swelling - Lethal factor cleaves protein kinases. - Blocks immune system from attacking Figure 25.21C

  15. Endotoxins Made only by Gram-negative bacteria Present in lipopolysaccharide of outer membrane - Lipid A released as bacteria die - Causes massive release of cytokine from host cells - Can trigger fever, shock, and death Figure 25.22

  16. Figure 25.31

  17. Figure 25.32

  18. Figure 25.29

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