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Category: Bacterial Pathogenesis
Escherichia coli, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817541/9781555813420_Chap04-1.gif /docserver/preview/fulltext/10.1128/9781555817541/9781555813420_Chap04-2.gifAbstract:
This chapter discusses six pathogenic or putative pathogenic groups of diarrheal Escherichia coli that are incapable of causing infection outside the gastrointestinal (GI) tract in detail. Commonly used acronyms for these groups are enteroinvasive E. coli (EIEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), Shiga toxin-producing E. coli (STEC, also known as enterohemorrhagic E. coli (EHEC), enteroaggregative E. coli (EAEC), and diffuse adhering E. coli(DAEC). E. coli strains involved in extraintestinal infections are related by the presence of specific virulence traits, and extraintestinal pathogenic E. coli (ExPEC) has been proposed for these strains. Molecular studies where DNA containing the alpha-hemolysin gene of one isolate has been recombined into a nonhemolytic fecal isolate have resulted in the recipient developing enhanced virulence in the rat peritonitis model. Production of cytotoxic necrotizing factor (CNF), a recently described virulence-associated factor, may also be associated with bacteremic E. coli strains. The K1 capsule is the major virulence determinant in E. coli strains, causing neonatal meningitis. GI disease involves the oral ingestion of pathogenic E. coli strains, with their subsequent colonization and infection of the small intestine and/or colon. Susceptibility testing of cysteine-requiring E. coli auxotrophs isolated from the urinary tract or other extraintestinal sites does not require supplementation for accurate results.
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Schematic representation of adherence patterns representing EPEC (localized), EAEC (aggregative), and DAEC (diffuse) types.
Schematic representation of adherence patterns representing EPEC (localized), EAEC (aggregative), and DAEC (diffuse) types.
(Right) Normal Y1 sheet; (left) Y1 cells exposed to heat-labile toxin (LT) for 24 h.
(Right) Normal Y1 sheet; (left) Y1 cells exposed to heat-labile toxin (LT) for 24 h.
(A) Normal Vero cell sheet; (B) Vero cells exposed to Shiga toxin (Stx) for 48 h.
(A) Normal Vero cell sheet; (B) Vero cells exposed to Shiga toxin (Stx) for 48 h.
Pellicle formation by three EAEC strains in Mueller-Hinton broth. The strongest reaction is indicated at the far left (with autoagglutination), and the weakest reaction is at the right.
Pellicle formation by three EAEC strains in Mueller-Hinton broth. The strongest reaction is indicated at the far left (with autoagglutination), and the weakest reaction is at the right.