1. Medical Technology Department, Faculty of Science, Islamic University-Gaza MB M ICRO B IOLOGY Dr. Abdelraouf A. Elmanama Ph. D Microbiology 2008 Chapter 15 Microbial Mechanisms of Pathogenicity

2. 2008 Microbial Mechanisms of Pathogenicity PathogenicityThe ability to cause disease VirulenceThe extent of pathogenicity

3. 2008 Mucous membranes Skin Parenteral route Portals of Entry

4. 2008 ID 50 : Infectious dose for 50% of the test population LD 50 : Lethal dose (of a toxin) for 50% of the test population Numbers of Invading Microbes

5. 2008 Bacillus anthracis Portal of entryID 50 Skin10-50 endospores Inhalation10,000-20,000 endospores Ingestion250,000-1,000,000 endospores

6. 2008 Adhesions/ligands bind to receptors on host cells GlycocalyxStreptococcus mutans FimbriaeEscherichia coli M proteinStreptococcus pyogenes Opa proteinNeisseria gonorrhoeae Tapered endTreponema pallidum Adherence

7. 2008 CoagulaseCoagulate blood KinasesDigest fibrin clots HyaluronidaseHydrolyses hyaluronic acid CollagenaseHydrolyzes collagen IgA proteasesDestroy IgA antibodies SiderophoresTake iron from host iron- binding proteins Antigenic variationAlter surface proteins Enzymes

8. 2008 Penetration into the Host Cell Figure 15.2

9. 2008 Toxins ToxinSubstances that contribute to pathogenicity ToxigenicityAbility to produce a toxin ToxemiaPresence of toxin the host's blood ToxoidInactivated toxin used in a vaccine AntitoxinAntibodies against a specific toxin

10. 2008 Endotoxin Figure 15.4b

11. 2008 Exotoxin SourceMostly Gram + Metabolic productBy-products of growing cell ChemistryProtein Fever?No Neutralized by antitoxinYes LD 50 Small

12. 2008 A-B toxins or type III toxins Exotoxins Figure 15.5

13. 2008 Superantigens or type I toxins Cause an intense immune response due to release of cytokines from host cells Fever, nausea, vomiting, diarrhea, shock, death Exotoxins

14. 2008 Membrane-disrupting toxins or type II toxins Lyse host’s cells by: Making protein channels in the plasma membrane (e.g., leukocidins, hemolysins) Disrupting phospholipid bilayer Exotoxins

15. 2008 Exotoxins Exotoxin Lysogenic conversion Corynebacterium diphtheriae A-B toxin. Inhibits protein synthesis. + Streptococcus pyogenes Membrane-disrupting. Erythrogenic. + Clostridium botulinumA-B toxin. Neurotoxin+ C. tetaniA-B toxin. Neurotoxin Vibrio choleraeA-B toxin. Enterotoxin+ Staphylococcus aureusSuperantigen. Enterotoxin.

16. 2008 Exotoxins Figure 15.4a

17. 2008 Endotoxins Figure 15.6

18. 2008 Endotoxins SourceGram– Metabolic productPresent in LPS of outer membrane ChemistryLipid Fever?Yes Neutralized by antitoxinNo LD 50 Relatively large

19. 2008 Cytopathic Effects of Viruses Table 15.4

20. 2008 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 Ergot toxin Claviceps Pathogenic Properties of Fungi

21. 2008 Aflatoxin Aspergillus Mycotoxins Neurotoxins: Phalloidin, amanitin Amanita Pathogenic Properties of Fungi

22. 2008 Presence of protozoa Protozoan waste products may cause symptoms Avoid host defenses by Growing in phagocytes Antigenic variation Pathogenic Properties of Protozoa

23. 2008 Use host tissue Presence of parasite interferes with host function Parasite's metabolic waste can cause symptoms Pathogenic Properties of Helminths

24. 2008 Neurotoxins produced by dinoflagellates Saxitoxin Paralytic shellfish poisoning Pathogenic Properties of Algae

25. 2008 Respiratory tract Coughing, sneezing Gastrointestinal tract Feces, saliva Genitourinary tract Urine, vaginal secretions Skin Blood Biting arthropods, needles/syringes Portals of Exit

26. 2008 Mechanisms of Pathogenicity Figure 15.9