Abstract
Background
A cluster of E. coli O157:H7 hemorrhagic colitis was identified in metro Edmonton, Alberta through notifiable disease surveillance in late 2002.
Methods
Environmental health officers collected food histories and clinical information from cases in the cluster. The provincial public health laboratory conducted pulsed field gel electrophoresis (PFGE) analysis on E. coli O157:H7 isolates from cluster cases. Public health and food regulatory agencies conducted an investigation when a food source (unpasteurized gouda cheese) was implicated.
Results
PFGE analysis revealed an “outbreak” profile in 13 cases. Onset dates for the outbreak cases ranged between October 2002 and February 2003. Two cases, aged 22 months and 4 years, developed hemolytic uremic syndrome as a result of their infection. Consumption of unpasteurized gouda cheese produced at a local dairy farm was reported by 12 of 13 outbreak cases in the 2 to 8 days prior to illness. E. coli O157:H7 was isolated from 2 of 26 cheese samples manufactured by the implicated producer. The cheese isolates had indistinguishable FGE profiles as compared with outbreak case isolates. Implicated cheese was found to be contaminated with E. coli O157:H7 104 days after production, despite having met regulated microbiological and aging requirements.
Conclusion
To our knowledge, this is the first confirmed outbreak of E. coli O157:H7 infection in Canada associated with raw milk hard cheese. A review of federal legislation vis-à-vis raw milk hard cheese may be in order.
MeSH terms: Escherichia coli O157, hemolytic-uremic syndrome, disease outbreaks, cheese
Résmé
Contexte
Vers la fin de 2002, le système de surveillance des maladies à déclaration obligatoire a relevé une concentration de cas de colite hémorragique causés par Escherichia coli O157:H7 dans le Grand Edmonton, en Alberta.
Méthode
Des hygiénistes du milieu ont recueilli les antécédents alimentaires et cliniques des cas relevés. Le laboratoire provincial de dépistage sanitaire a analysé par électrophorèse sur gel en champs pulsé (EGCP) des isolats de E. coli O157:H7 parmi ces cas. Les organismes de santé publique et de réglementation des aliments ont fait enquête lorsqu’une source de nourriture (du gouda non pasteurisé) a été mise en cause.
Résultats
L’EGCP a révélé une séquence apparentée à une éclosion dans 13 cas. Les dates d’apparition des cas liés à l’éclosion se situaient entre octobre 2002 et février 2003. Deux cas, l’un âgé de 22 mois et l’autre de quatre ans, ont présenté un syndrome hémolytique et urémique dû à l’infection. Douze des 13 cas liés à l’éclosion ont dit avoir consommé du gouda non pasteurisé fabriqué dans une ferme laitière locale au cours d’une période de deux à huit jours avant leur maladie. On a isolé E. coli O157:H7 dans deux des 26 échantillons de fromage fabriqués par la ferme en question. Les séquences EGCP des isolats du fromage étaient identiques à ceux des isolats des cas liés à l’éclosion. Le fromage en question avait été contaminé, 104 jours après sa fabrication, par E. coli O157:H7, bien que la ferme ait respecté les exigences réglementaires en matière microbiologique et d’affinage.
Conclusion
À notre connaissance, il s’agit de la première éclosion confirmée du colibacille O157:H7 au Canada associée à du fromage au lait cru à pâte dure. Un examen de la législation fédérale sur le fromage au lait cru à pâte dure pourrait être indiqué.
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