Stx2 from enterohemorrhagic Escherichia coli O157:H7 promotes colonization in the intestine of cattle

Abstract

Cattle act as the main reservoir for enterohemorrhagic Escherichia coli O157:H7, a bacterium that causes serious human disease outbreaks. It is currently not clear which bacterial or animal factors contribute to E. coli O157:H7 colonization in cattle. We recently identified mucosal hemorrhages in the jejunum, ileum and colon of persistent shedding cattle that were associated with E. coli O157:H7 colonization. This suggested that E. coli O157:H7-secreted cytotoxins may be involved in the E. coli O157:H7 colonization process. Further studies confirmed that E. coli O157:H7-secreted cytotoxins were toxic to cattle enterocytes and enhanced E. coli O157:H7 colonization of intestinal tissues. The current study examined the contribution of Stx2 to the earlier reported E. coli O157:H7- associated mucosal damage and secreted cytotoxin activity. Stx2 was not cytotoxic to enterocytes, but did enhance E. coli O157:H7 adherence to intestinal tissues in cattle. This is the first report of an E. coli O157:H7 virulence factor that can directly influence the E. coli O157:H7 colonization process in cattle. Key words: Stx2, Escherichia coli O157:H7, cattle, intestine, colonization