1. Foodborne Pathogen Reference Unit, Health Protection Agency (HPA), Centre for Infections, London NW9 5EQ, UK
2. Paediatric Intensive Care Unit, Great Ormond Street Hospital, Great Ormond Street, London, UK
3. Department of Microbiology, Great Ormond Street Hospital, Great Ormond Street, London, UK
4. North East & Central London Health Protection Unit, London, UK
5. Department of Medical Microbiology, St George's Hospital, London, UK
6. Surrey and Sussex Health Protection Unit, Leatherhead, Surrey, UK
7. Health Protection Agency Regional Microbiology Network, London, UK