The paper presents the results of etiological interpretation of the outbreak of Escherichia coli O157-induced enteric infection complicated by hemolytic uremic syndrome in Omsk in spring 2009. Seventeen infants aged 5 months to 2.5 years were examined; of them 9 patients were on hemodialysis. The diagnosis was verified in 7 children, by isolating verotoxin after fecal enrichment on the concentrating nutrient RIDA Enrichment Bouillon medium containing bile salts and mitomycin C, E. coli O157:H7 cultures on the sorbitol medium and/or by identifying E. coli O157 DNA. Six (4 having verotoxin) infants were found to have rotavirus and noro-virus antigens or DNA/RNA, which may make a contribution into the development of mixed infection and increase the risk of complications.