Chapter 15: Microbial Mechanisms of Pathogenicity

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Chapter 15: Microbial Mechanisms of Pathogenicity

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1. Pathogenicity: The ability to cause disease Virulence: The extent of pathogenicity Chapter 15: Microbial Mechanisms of Pathogenicity

2. Portals of Entry Mucous membranes Skin Parenteral route Preferred portal of entry

3. Numbers of Invading Microbes ID50: Infectious dose for 50% of the test population LD50: Lethal dose (of a toxin) for 50% of the test population

4. Bacillus anthracis

5. Toxins

6. Adherence Adhesins/ligands bind to receptors on host cells Glycocalyx: Streptococcus mutans Fimbriae: Escherichia coli M protein: Streptococcus pyogenes

7. Capsules Prevent phagocytosis Streptococcus pneumoniae Haemophilus influenzae Bacillus anthracis

8. Cell Wall Components M protein resists phagocytosis Streptococcus pyogenes Opa protein inhibits T helper cells Neisseria gonorrhoeae Mycolic acid (waxy lipid) resists digestion Mycobacterium tuberculosis

9. Enzymes Coagulase: Coagulates fibrinogen Kinases: Digest fibrin clots Hyaluronidase: Hydrolyzes hyaluronic acid Collagenase: Hydrolyzes collagen IgA proteases: Destroy IgA antibodies

10. Membrane Ruffling

11. Antigenic Variation Alter surface proteins

12. Invasins Salmonella alters host actin to enter a host cell Use actin to move from one cell to the next Listeria Penetration into the Host Cell Cytoskeleton

13. Using the Hostís Nutrients: Siderophores Use hostís iron

14. Direct Damage Disrupt host cell function Produce waste products Toxins

15. The Production of Toxins Toxin: Substance that contributes to pathogenicity Toxigenicity: Ability to produce a toxin Toxemia: Presence of toxin in the host's blood Toxoid: Inactivated toxin used in a vaccine Antitoxin: Antibodies against a specific toxin

16. Exotoxins and Endotoxins

17. The Action of an A-B Exotoxin

18. Membrane-Disrupting Toxins Lyse hostís cells by Making protein channels in the plasma membrane Leukocidins Hemolysins Streptolysins Disrupting phospholipid bilayer

19. Superantigens Cause an intense immune response due to release of cytokines from host cells Symptoms: fever, nausea, vomiting, diarrhea, shock, and death

20. Exotoxin

21. Exotoxins & Lysogenic Conversion

22. Endotoxins

23. Endotoxins and the Pyrogenic Response

24. LAL Assay Limulus amoebocyte lysate assay Amoebocyte lysis produces a clot Endotoxin causes lysis

25. Inflammation Following Eye Surgery Patient did not have an infection The LAL assay of solution used in eye surgery What was the cause of the eye inflammation? What was the source?

26. Cytopathic Effects of Viruses

27. Cytopathic Effects of Viruses

28. Pathogenic Properties of Fungi Fungal waste products may cause symptoms Chronic infections provoke an allergic response Tichothecene toxins inhibit protein synthesis Fusarium Proteases Candida, Trichophyton Capsule prevents phagocytosis Cryptococcus

29. Pathogenic Properties of Fungi Ergot toxin Claviceps Aflatoxin Aspergillus Mycotoxins Neurotoxins: Phalloidin, amanitin Amanita

30. Pathogenic Properties of Protozoa Presence of protozoa Protozoan waste products may cause symptoms Avoid host defenses by Growing in phagocytes Antigenic variation

31. Pathogenic Properties of Helminths Use host tissue Presence of parasite interferes with host function Parasite's metabolic waste can cause symptoms

32. Pathogenic Properties of Algae Paralytic shellfish poisoning Dinoflagellates Saxitoxin

33. Portals of Exit Respiratory tract Coughing and sneezing Gastrointestinal tract Feces and saliva Genitourinary tract Urine and vaginal secretions Skin Blood Biting arthropods and needles or syringes

34. Mechanisms of Pathogenicity

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