Laboratory investigation of enteroaggregative Escherichia coli O untypeable:H10 associated with a massive outbreak of gastrointestinal illness

A massive outbreak of gastrointestinal illness occurred in Tajimi city, Gifu prefecture, in June of 1993 in which 2,697 children in elementary and junior high schools developed severe diarrhea, Stool specimens from 30 children with severe protracted diarrhea were studied, Twenty-seven strains of enteroaggregative Escherichia coli (EAggEC) isolated from 12 of 30 patients all belonged to the same serotype, O untypeable (OUT): H10, and showed the same biochemical characteristics and antibiotic susceptibility pattern, These strains were negative for the virulence factors of the four standard categories of diarrheagenic E. coli (enterotoxigenic, enteropathogenic, enteroinvasive, and enterohemorrhagic). However, the isolates showed an aggregative pattern of adherence to HEp-2 cells and had a 60-MDa plasmid and an astA gene, which encodes heat-stable enterotoxin-l production. These data suggested that the EAggEC serotype OUT:H10 was associated with this massive outbreak of gastrointestinal illness.