HeLa cell adherence, actin aggregation, and invasion by nonenteropathogenic Escherichia coli possessing the eae gene

Enteropathogenic Escherichia coli (EPEC) produce diarrhea in humans by a mechanism that involves close adherence to epithelial cells in the intestine and colon. Close adherence is associated with effacement of microvilli and condensation of actin beneath the bacteria, a process termed attaching/effacing adherence. Attaching/effacing adherence of EPEC occurs in vitro in tissue culture, simplifying the study of the molecular genetics of this process. An EPEC gene (eae) necessary for attaching/effacing adherence was recently characterized. Enterohemorrhagic E. coli and the rabbit-specific RDEC-1 strain adhere in a like fashion in vivo and hybridize with eae. However, these strains adhere poorly to tissue culture cells, complicating the in vitro study of attaching/effacing adherence. In order to develop an in vitro model for the study of attaching/effacing activity of non-EPEC bacteria, a plasmid encoding the F1845 adhesin of an E. coli strain (C1845) isolated from a patient with diarrhea was transformed into RDEC-1 and enterohemorrhagic E. coli. The transformed strains adhered in a diffuse pattern to HeLa cells, and they aggregated HeLa cell actin at points of adherence in the fluorescein-isothiocyanate-labeled phalloidin assay. They also invaded HeLa cells in a gentamicin invasion assay, although not to the extent seen with EPEC. The construction of adherent non-EPEC strains facilitates the molecular study of the attaching/effacing properties and invasiveness of these strains in tissue culture models.