1 Health Protection Research Unit in Healthcare Associated Infection and Antimicrobial Resistance, Imperial College London, London, W12 0HS, UK; Infection Control Programme, Geneva University Hospitals, Geneva, Switzerland. Electronic address: mohamed.abbas@hcuge.ch.
2 Health Protection Research Unit in Healthcare Associated Infection and Antimicrobial Resistance, Imperial College London, London, W12 0HS, UK.
3 Health Protection Research Unit in Healthcare Associated Infection and Antimicrobial Resistance, Imperial College London, London, W12 0HS, UK; Imperial College Healthcare NHS Trust, London, UK.