MEDizzy - Escherichia coli is a facultative anaerobe that colonizes

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Infections due to Neisseria and others

Escherichia coli is a facultative anaerobe that colonizes the human intestine. At least six pathotypes have been identified that can cause diarrhea, urinary tract infections (UTIs), and nosocomial illness. Which of the following does NOT contribute to the pathogenicity of the various E. coli strains?

ExplanationSeveral distinct pathotypes of E. coli are known to induce a wide range of disease. Among the common virulence factors shared by all pathotypes of E. coli is the catalase enzyme, which helps protect the organism from host respiratory burst defenses by reducing hydrogen peroxide to water and oxygen. The enterotoxigenic pathotypes of E. coli also produce heat-labile and heat-stable enterotoxins that bind to intestinal cells and cause the efflux of chloride, sodium, and water into the intestinal lumen, resulting in diarrhea. The enterohemorrhagic pathotypes (among which serotype O157:H7 is the most important) cause diarrhea by binding to the apical surface of enterocytes, which results in destruction of microvilli (described histologically as the attaching and effacing effect). In addition, these enterohemorrhagic strains share with Shigella the ability to release Shiga toxin, which induces cell death and is responsible for the serious systemic complications of infection with these strains, including hemolytic-uremic syndrome (HUS). Coagulase production is not a significant means of pathogenesis for E. coli.