Survey of cytotoxin production among Escherichia coli strains characterized as enteropathogenic (EPEC) by serotyping and presence of EPEC adherence factor (EAF) sequences.

A total of 108 Escherichia coli strains characterized as enteropathogenic (EPEC) by serotyping and the presence of EPEC adherence factor (EAF) sequences were examined for cytotoxin production by cell line assays and colony hybridization with Shiga-like toxin (SLT) probes. Cytolethal distending toxin (CLDT) production was found in three (2.8%) strains belonging to serotype O86:H34, while one O111ab:NM strain hybridized with a SLT-II probe but did not express any cytotoxic activity. All four strains showed localized adherence to HeLa cells and hybridized to an E. coli attaching-effacing gene (eae) probe. The CLDT-producing strains had multiple plasmids and some were present in all strains, including a plasmid of approximately 54 MDa that hybridized with the EAF probe.