[Enteroinvasive Escherichia coli O121: H- isolated from travellers' diarrhea]

A lactose slow-fermenting, non motile Escherichia coli strain was isolated from a diarrheal patient returning from Indonesia. Examination of virulence of the strain showed that it penetrated into tissue culture cells, and were positive in Serény test and enzyme-linked immunosorbent assay for detection of enteroinvasive E. coli. A large plasmid responsible for virulence was also detected. Thus the strain was confirmed to be a typical enteroinvasive E. coli. Analysis of O serotype using the antisera against E. coli O1-O170 revealed that the strain had O121 antigen, whose antiserum is not included in the commercial serotyping kit for the diagnosis of diarrheagenic E. coli.