1. Department of Medicine, University of Cambridge , Cambridge , UK
2. Cambridge Clinical Microbiology and Public Health Laboratory, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke’s Hospital , Hills Road , Cambridge CB2 0QQ, UK
3. Department of Infectious Diseases, Cambridge University Hospitals NHS Foundation Trust , Cambridge , UK
4. MRC Biostatistics Unit, Cambridge University , Cambridge , UK
5. Cambridge Colorectal Unit, Cambridge University Hospitals NHS Foundation Trust , Cambridge , UK
6. Department of Surgery, University of Cambridge , Cambridge , UK
7. Department of General Surgery, Cambridge University Hospitals NHS Foundation Trust , Cambridge , UK
8. Department of Infection, Prevention and Control, Cambridge University Hospitals NHS Foundation Trust , Cambridge , UK
9. Department of Allergy, Cambridge University Hospitals NHS Foundation Trust , Cambridge , UK