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)
9.
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
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