1. Chapter 15 Microbial Mechanisms of Pathogenicity

5. Bacillus anthracis 250,000-1,000,000 endospores Ingestion 10,000-20,000 endospores Inhalation 10-50 endospores Skin ID 50 Portal of entry

8. Penetration into the Host Cell Figure 15.2 Invasins – rearrange actin fibers associated with host cell membrane Salmonella, E. coli Causes membrane ‘ruffling” – result of cytoskeletal disruption Microbe sinks into ruffle and is Ingested by cell. Actin can be used as propulsion once inside host cell (s higella spp)

10. Exotoxin – many are enzyme-like Small LD 50 Yes (good antigen) Neutralized by antitoxin No (mostly…except type 1) Fever? Protein Chemistry By-products of growing cell Metabolic product Mostly Gram + Source

14. Exotoxins Superantigen. Enterotoxin. • Staphylococcus aureus + A-B toxin. Enterotoxin • Vibrio cholerae A-B toxin. Neurotoxin • C. tetani + A-B toxin. Neurotoxin • Clostridium botulinum + Membrane-disrupting. Erythrogenic. • Streptococcus pyogenes + A-B toxin. Inhibits protein synthesis. • Corynebacterium diphtheriae Lysogenic conversion Exotoxin

15. Exotoxins Figure 15.4a

16. Endotoxin Figure 15.4b

17. Endotoxins Figure 15.6 (A cytokine) TNF – tumor necrosis factor – another cytokine secreted by phagocytes– damages capillaries

18. Endotoxins Relatively large LD 50 No (poor antigen) Neutralized by antitoxin Yes Fever? Lipid-polysaccharide Chemistry Present in LPS of outer membrane Metabolic product Gram– Source

19. Test for endotoxin presence Endotoxins are heat resistant, may persist on surfaces. LAL- Limulus Amoebocyte Lysate – presence of minute amounts of endotoxin lyses amoebocytes which release lysate Lysate then causes coagulation of the media

20. Cytopathic Effects of Viruses Table 15.4

27. Mechanisms of Pathogenicity Figure 15.9