1. Department of Nursing, Barts and the London NHS Trust, London, UK
2. Department of Medical Microbiology, Barts and the London NHS Trust, London E1 2ES, UK
3. Department of Infection Prevention and Control, Birmingham Community Health Care Trust, Birmingham, UK
4. School of Health Science, City University, London, UK
5. The Milk Bank, Queen Charlotte’s and Chelsea Hospital, London, UK