[An outbreak of gastroenteritis possibly caused by Escherichia coli O167:H9]

An outbreak of gastroenteritis involving a total of 256 patients (49.7%) among 515 persons occurred at a primary and secondary school in Agatsuma Town, Gunma Prefecture between the 23rd and 28th of June 1988. The majority of the cases occurred within the first 4 days. The main symptoms were abdominal pain (81.6%), diarrhea (57.0%) and headache (40.2%). In most cases, the stools were watery and occasionally mucous. Although food-borne infection was strongly suggested epidemiological evidence did not incriminate any foods as the cause of the outbreak. In the bacteriological study on stool specimens from 25 patients, Escherichia coli O167:H9 was isolated from 20 of these specimens, virtually in pure culture. The isolates of the E. coli serovar were negative for recognized diarrheagenic virulence properties: production of heat-labile and heat-stable enterotoxins, enteroinvasion, and production of Shiga-like toxin. When the HEp-2 cell-adherence test was used, however, they exhibited localized adherence. All the strains were demonstrated to carry 56 Md plasmids that presumably mediate the production of the adherence factor.