1. Department of Cardiology, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK
2. Department of Microbiology, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK
3. Centre for Infections, Health Protection Agency, 61 Colindale Avenue, London NW9 5HT, UK
4. Department of Cardiac Surgery, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK