The localized adherence pattern of an atypical enteropathogenic Escherichia coli is mediated by intimin omicron and unexpectedly promotes HeLa cell invasion.

Enteropathogenic Escherichia coli (EPEC) forms attaching and effacing lesions in the intestinal mucosa characterized by intimate attachment to the epithelium by means of intimin (an outer membrane adhesin encoded by eae). EPEC is subgrouped into typical (tEPEC) and atypical (aEPEC); only tEPEC carries the EAF (EPEC adherence factor) plasmid that encodes the bundle-forming pilus (BFP). Characteristically, after 3 h of incubation, tEPEC produces localized adherence (LA) (with compact microcolonies) in HeLa/HEp-2 cells by means of BFP, whereas most aEPEC form looser microcolonies.

Characterization of atypical enteropathogenic Escherichia coli strains that express typical localized adherence in HeLa cells in the absence of the bundle-forming pilus.

The characterization of nine atypical enteropathogenic Escherichia coli strains expressing localized adherence in HeLa cells in the absence of the bundle-forming pilus revealed a diversity of serotypes, plasmids, and virulence genes. Although the strains lacked known E. coli adhesin genes, the identification of new adhesins could contribute to the characterization of similar enteropathogenic E.