Research – O148 Shiga toxin-producing Escherichia coli outbreak: microbiological investigation as a useful complement to epidemiological investigation

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An outbreak of Shiga toxin-producingEscherichia coli(STEC) O148 infection occurred among weddingattendees in France in June 2002. A retrospective cohort study was performed and ten cases wereidentified, including two adults with haemolytic uraemic syndrome (HUS). The analytical studyrevealed that > 80%of affected individuals had eaten lightly roasted mutton and poultry paˆte ́, but onlythe consumption of paˆte ́tended to be associated with illness (relative risk 3.4; 95%CI 0.8–14.4). Left-overs (cooked mutton and raw offal) and processed foods (paˆte ́) from the same batches as served at theparty were sampled. Human, food and environmental samples were examined for the Shiga toxin (stx)gene and virulence traits by PCR.Stx-positive samples were cultured for STEC. HUS cases were testedfor serum antibodies against 26 major STEC serogroups. An STEC O26 strain (stx1,eae,ehxA) wasisolated from one case with diarrhoea, and an STEC O148 strain (stx2c) from one case of HUS. Serumantibodies against O26 were not detected in either of these patients; antibodies against O148 were nottested. Three STEC strains were isolated from the mutton and the offal (stx2c, O148), and two from thepaˆte ́(stx2c, O-X and O-Y). The isolates from the mutton were indistinguishable from the humanstx2cisolate, whereas the paˆte ́isolates differed. Although four different STEC strains were identified inpatients and foods, the results of molecular subtyping, in conjunction with analysis of food consumptionpatterns, strongly suggested that this outbreak was caused by mutton contaminated with STEC O148.

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