Epidemiology of a large restaurant-associated outbreak of Shiga toxin-producing Escherichia coli O111:NM.

ABSTRACT

In August 2008, a large outbreak of Shiga toxin-producing Escherichia coli (STEC) O111NM infections associated with a buffet-style restaurant in rural Oklahoma was identified. A case-control study of restaurant patrons and a retrospective cohort study of catered event attendees were conducted coupled with an environmental investigation to determine the outbreak's source and mode of transmission. Of 1823 persons interviewed, 341 (18·7%) met the outbreak case definition; 70 (20·5%) were hospitalized, 25 (7·3%) developed haemolytic uraemic syndrome, and one died. Multiple food items were significantly associated with illness by both bivariate and multivariate analyses, but none stood out as a predominant transmission vehicle. All water, food, and restaurant surface swabs, and stool cultures from nine ill employees were negative for the presence of Shiga toxin and E. coli O111NM although epidemiological evidence suggested the outbreak resulted from cross-contamination of restaurant food from food preparation equipment or surfaces, or from an unidentified infected food handler.