[1] Univ London Imperial Coll Sci Technol & Med, Hammersmith Hosp, Natl Ctr Infect Prevent & Management, London W12 0HS, England
[2] Hlth Protect Agcy, Publ Hlth Strategy Div, Healthcare Associated Infect & Antimicrobial Res, London NW9 5HT, England
[3] St George Hosp, Paediat Infect Dis Unit, London SW17 0QT, England
[4] Gloucestershire Royal Hosp, Dept Microbiol, Primary Care Unit, Hlth Protect Agcy, Gloucester GL1 3NN, England
[5] Univ Manchester, Sch Pharm & Pharmaceut Sci, Manchester M13 9PT, Lancs, England
[6] Manchester Acad Hlth Sci Ctr, Manchester M13 9PT, Lancs, England