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Pork Implicated in a Shiga Toxin-producing Escherichia coli O157:H7 Outbreak in Ontario, Canada

  • Quantitative Research
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Abstract

Objectives

To describe an outbreak of Shiga toxin-producing Escherichia coli (STEC) O157:H7 infection following a four-day family gathering in Ontario. This is the first published account of a STEC O157 outbreak in Canada linked to consumption of pork.

Methods

The outbreak investigation included interviews with food handlers and other key associated persons, inspection of food preparation premises, traceback investigations, case finding, analysis of data from an outbreak questionnaire, and laboratory analysis of samples collected from various sources associated with the outbreak.

Results

Several meals, including pork from a pig roast, were served to the 59 attendees, 29 of whom developed gastrointestinal illness following the event. Six cases developed bloody diarrhoea and seven were hospitalized. Leftover pork served the day after the pig roast was the item most significantly associated with an increased risk of illness (p<0.001). STEC O157:H7 was isolated from 11 of the 29 ill attendees, and also from the pork. By pulse-field gel electrophoresis (PFGE), all STEC O157:H7 pork isolates were either identical or closely related to the 11 clinical isolates. No STEC was detected in any other samples. Three Clostridium perfringens isolates, unrelated by PFGE, were obtained from two STEC-positive cases and the pork.

Conclusion

This outbreak highlights the need for increased awareness of pork as a potential source of STEC O157 infection, and for enhanced education regarding the safe handling, cooking and storage of food, specifically where large cuts of meat are cooked outdoors at events such as pig roasts, a cultural norm in some communities.

Résumé

Objectif

Décrire une éclosion d’infections à Escherichia coli producteur de toxine dysentérique (STEC) O157:H7 après une réunion familiale de quatre jours en Ontario. Il s’agit du premier compte rendu publié d’une éclosion de STEC O157 liée à la consommation de porc au Canada.

Méthode

L’enquête sur l’éclosion a compris des entretiens avec les manipulateurs d’aliments et autres personnes liées, l’inspection des installations de préparation des aliments, des enquêtes de retraçage, la recherche des cas, l’analyse des données d’un questionnaire sur l’éclosion et des analyses de laboratoire sur des échantillons prélevés de diverses sources associées à l’éclosion.

Résultats

Plusieurs repas, y compris du cochon cuit à la broche, ont été servis aux 59 participants, dont 29 ont contracté une maladie gastrointestinale après la fête. Six cas ont eu une diarrhée sanglante et sept ont été hospitalisés. Les restes de porc servis le lendemain de la cuisson à la broche ont présenté la corrélation la plus significative avec le risque accru de maladie (p<0,001). STEC O157:H7 a été isolé chez 11 des 29 participants malades, ainsi que dans le porc. Selon l’électrophorèse sur gel en champs pulsé (EGCP), tous les isolats de STEC O157:H7 du porc étaient soient identiques, soit étroitement liés aux 11 isolats cliniques. La présence de STEC n’a été détectée dans aucun autre échantillon. Trois isolats de Clostridium perfringens, non liés selon l’EGCP, ont été obtenus à partir du porc et de deux cas positifs pour le STEC.

Conclusion

Cette éclosion montre qu’il faut davantage surveiller le porc comme source d’infection potentielle par le pathogène STEC O157 et sensibiliser la population aux techniques de manipulation, de cuisson et d’entreposage sans danger des aliments, en particulier lorsque de grandes coupes de viande, comme le porc, sont cuites à l’extérieur à la broche (ce qui fait partie de la culture de certaines collectivités).

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Author information

Authors and Affiliations

  1. Wellington-Dufferin-Guelph Public Health, 600 Southgate Drive, Guelph, ON, N1G 4P6, Canada

    Lise A. Trotz-Williams BVetMed, MSc, PhD, Nicola J. Mercer MD, MPH, FRCPC & Janice M. Walters BScN, MEd, MPH

  2. Public Health Laboratories - Toronto, Public Health Ontario, Toronto, ON, Canada

    Anne M. Maki MLT

  3. Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, Guelph, ON, Canada

    Roger P. Johnson MVSc, PhD

Authors
  1. Lise A. Trotz-Williams BVetMed, MSc, PhD
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  2. Nicola J. Mercer MD, MPH, FRCPC
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  3. Janice M. Walters BScN, MEd, MPH
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  4. Anne M. Maki MLT
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  5. Roger P. Johnson MVSc, PhD
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Corresponding author

Correspondence to Lise A. Trotz-Williams BVetMed, MSc, PhD.

Additional information

Sources of support: PHAC; Ontario Ministry of Agriculture, Food & Rural Affairs; Public Health Ontario; Ontario Ministry of Health and Long-Term Care; Centers for Disease Control.

Conflict of Interest: None to declare.

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Trotz-Williams, L.A., Mercer, N.J., Walters, J.M. et al. Pork Implicated in a Shiga Toxin-producing Escherichia coli O157:H7 Outbreak in Ontario, Canada. Can J Public Health 103, e322–e326 (2012). https://doi.org/10.1007/BF03404434

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  • DOI: https://doi.org/10.1007/BF03404434

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