1. Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
2. National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
3. National Microbiology Laboratory, Public Health Agency of Canada, Guelph, Ontario, Canada
4. Centre for Foodborne, Environmental and Zoonotic Infectious Diseases, Public Health Agency of Canada, Guelph, Ontario, Canada
5. Ottawa Laboratory (Carling), Canadian Food Inspection Agency, Ottawa, Ontario, Canada
6. London Research and Development Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada; Department of Biology, University of Western Ontario, London, Ontario, Canada
7. Present address: Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Toronto, Canada
8. Public Health Ontario Laboratory, Toronto, Ontario, Canada