1. Department of Medical Microbiology, School of Medicine, University of Manchester, Clinical Sciences Building, Manchester Royal Infirmary, Manchester M13 9WL, United Kingdom
2. Health Protection Agency North West Laboratory, Clinical Science Building, Manchester Royal Infirmary, Manchester M13 9WZ, United Kingdom
3. Preston Microbiology Services, Royal Preston Hospital, Lancashire Teaching Hospitals NHS Foundation Trust, Sharoe Green Lane, Preston, Lancashire PR2 9HT, United Kingdom
4. Escherichia, Shigella, Yersinia, and Vibrio Reference Unit, Laboratory of Enteric Pathogens, Centre for Infections, 61 Colindale Avenue, London NW9 5HT, United Kingdom