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Mechanisms of Pathogenicity

Mechanisms of Pathogenicity - produced by Clostridium...

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Mechanisms of Pathogenicity - Invasion, virulence factors, damage to host cells - Direct damage may occur if the pathogen is able to "break into" host cells after attaching to them = This may be accomplished by the pathogen's inducing phagocytosis by host cells; later, the pathogen may break out to invade additional cells = Some pathogens have evolved to exploit phagocytosis as a mechanism for transport to tissues - Toxins are molecules that cause damage to host cells; bacteria that produce toxins are called toxigenic - Exotoxins are proteins released by pathogens; most are enzymes produced by Gram-positive bacteria (Tortoa et al., Table 15.2) = Cytotoxins affect the functions of host cells, often killing them; diphtheria toxin, produced by Corynebacterium diphtheriae, inhibits protein synthesis in eucaryotic cells (Tortora et al., Figure 15.4) = Neurotoxins interfere with normal nerve impulse transmission; examples are botulinum toxin,
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Unformatted text preview: produced by Clostridium botulinum, and tetanus toxin, produced by Clostridium tetani = Enterotoxins, such as the choleragen produced by Vibrio cholerae, interfere with fluid and electrolyte balance in gastrointestinal epithelium, leading to severe dehydration- Endotoxins are derived from lipopolysaccharides (LPS) from the cell walls of Gram-negative bacteria = Death of the bacterial cells leads to release of endotoxin, which is the lipid A portion of LPS = Endotoxin appears to act by causing release of interleukins (Tortora et al., Figure 15.5), which leads to a pyrogenic (fever-inducing) response by the host = If released in large amounts, endotoxins can lead to septic shock- Tortora et al. Figure 15.3 and Table 15.2 outline differentiation of exotoxins and endotoxin- Genes encoding production of exotoxins and other virulence factors may be encoded on plasmids or prophages carried by pathogenic bacteria...
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