Outbreak of Escherichia coli O157:H7 infection in a large family.

An outbreak of bloody and nonbloody diarrhoea caused by Escherichia coli O157:H7 including one case of haemolytic uraemic syndrome (HUS) and two cases of haemolytic anaemia, in five siblings (aged 2.5 to 11.3 years) and their playmate was investigated. Using sorbitol-MacConkey agar, colony blot hybridisation, and immunomagnetic separation, Shiga toxin 2-producing Escherichia coli O157:H7 was isolated from all children but the HUS patient; however, this patient had high immunoglobulin M antibody titres against Escherichia coli O157 lipopolysaccharide. Escherichia coli O157 isolates from all patients were indistinguishable in serotype, virulence properties, and genomic background, indicating that the same strain caused the infections. These data confirm the importance of person-to-person transmission.