Enterotoxigenicity and invasive capacity of “enteropathogenic” serotypes of Escherichia coli*

Forty-two strains of Escherichia coli that agglutinated in pools of antisera used to identify "enteropathogenic" serotypes were tested for heat-labile and heat-stable toxin production and for their ability to invade intestinal mucosa. None of the strains tested were enterotoxigenic or enteroinvasive as determined by the adrenal cell (heat-labile toxin), the suckling mouse (heat-stable toxin), or guinea pig eye (invasive capacity) assays. Our observations suggest that serotyping of E. coli is an unreliable method to identify isolates that are capable of causing gastroenteritis, at least as determined by available in vitro techniques.