BIOL 3P96 Lecture Notes - Lecture 14: Lethal Dose, Lipopolysaccharide, Median Lethal Dose
2 Aug 2015
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Lecture #14- bacterial pathogenesis: how microbes cause disease. * break in tissue allows organism access to new site. * loss of other microflora allows organism to bloom. Pathogen transmission four main modes of transmission airborne contact vehicle vector borne. Virulence refers to the intensity of disease produced by a pathogen. Virulence factors help bacteria to (1) invade the host, (2) cause disease, and (3) evade host defenses. Adherence factors: many pathogenic bacteria colonize mucosal sites by using pili (fimbriae) to adhere to cells. Invasion factors: surface components that allow the bacterium to invade host cells can be encoded on plasmids, but more often are on the chromosome. Number of organisms to colonize 50% of hosts. Number of organisms to kill 50% of hosts. Capsules: many bacteria are surrounded by capsules that protect them from opsonization and phagocytosis. Endotoxins: the lipopolysaccharide endotoxins on gram-negative bacteria cause fever, changes in blood pressure, inflammation, lethal shock, and many other toxic events.
