1. Department of Medical Microbiology, Royal London Hospital Trust, 37 Ashfield Street, London E1 1BB
2. Department of Oral Microbiology, St Bartholomew's and The Royal London School of Medicine and Dentistry, Turner Street, London E1 2AD
3. Gastrointestinal Science Research Unit, St Bartholomew's and The Royal London School of Medicine and Dentistry, 26 Ashfield Street, London E1 2AJ
4. Department of Epidemiology, St Bartholomew's and The Royal London School of Medicine and Dentistry, Turner Street, London E1 1BB