Outbreak of Escherichia coli O157 in a nursery: lessons for prevention

Objectives-To identify risk factors for transmission of verocytotoxin produ cing Escherichia coli O157 (VTECO157) and means of prevention. Study design-Outbreak investigation: retrospective cohort study. Setting-A nursery (child care centre) in North Wales. Subjects-Children attending (n = 104). Methods-Faeces were examined using sorbitol MacConkey agar (SMAC), with cef ixime, tellurite, and rhamnose; enrichment in modified tryptone soya broth; and immunomagnetic separation. Symptoms and exposure data were obtained fr om questionnaires to parents/guardians and children's toiletting and feedin g records kept at the nursery. Main outcome measure-A "case" was defined as a child with verocytotoxin pro ducing E coli O157 isolated from faeces, or a history of haemolytic uraemic syndrome (HUS) and antibodies to E coli O157 Lipopolysaccharide, during th e period 10 August to 30 September 1995. Results-The attack rate was 31 in 104. Two children developed HUS. There we re higher attack rates among girls friends who played together. Cases were more likely to attend the nursery more frequently. The mean number of recor ded bowel motions/child/half day was 0.51 in cases and 0.21 in well childre n. Child to staff ratios were high preceding and during the outbreak. Conclusions-A sick child is The most plausible source of infection with sub sequent person to person transmission. The record of children's toiletting discriminated between cases and well children and might have allowed earlie r detection of the outbreak. This simple record could be considered by othe r child care facilities as a means of giving early warning of problems with infectious intestinal diseases.