Escherichia coli O157: H7: An update on intestinal colonization and virulence mechanisms

Rodney A. Moxley

Research output: Contribution to journalReview articlepeer-review

56 Scopus citations


Cattle are a major reservoir of Escherichia coli O157:H7, an important zoonotic pathogen that causes hemorrhagic colitis and hemolytic uremic syndrome (HUS). Colonization of cattle occurs predominantly in the large intestine, and may especially target follicle-associated epithelium (FAE) in the terminal rectum. Bacterial colonization involves induction of attaching–effacing (A/E) lesions, mediated by type III secreted proteins and an outer membrane protein called intimin. ToxB, encoded on plasmid pO157, contributes to adherence of E. coli O157:H7 through promotion of the production and/or secretion of type III secreted proteins. Production of type III secreted proteins and intestinal colonization appear to involve quorum-sensing mechanisms. In the human host, E. coli O157:H7 may have a preference for FAE in the distal small intestine. The H7 flagellum induces production of chemokines such as interleukin 8, and neutrophilic infiltration of the intestinal mucosa, which in turn may enhance Shiga toxin (Stx) uptake across the intestinal epithelium. Both Stx and cytokine responses play critical roles in the induction of the vascular lesions that underlie hemorrhagic colitis and HUS. In cattle, Stx binds to intestinal crypt cells and submucosal lymphocytes but not vascular endothelium. The role played by Stx in cattle may be to suppress mucosal immunity, yet enhance other effects that promote intestinal colonization.

Original languageEnglish (US)
Pages (from-to)15-33
Number of pages19
JournalAnimal health research reviews
Issue number1
StatePublished - Jun 2004


  • Escherichia coli
  • O157:H7
  • colonization
  • enterohemorrhagic strains
  • virulence

ASJC Scopus subject areas

  • Animal Science and Zoology


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