1 Gloucestershire Hospitals NHS Foundation Trust, Gloucestershire Royal Hospital, Gloucester, UK.
2 University Hospitals Birmingham NHS Foundation Trust, Queen Elizabeth Hospital Birmingham, Edgbaston, Birmingham, UK.
3 Gloucestershire Hospitals NHS Foundation Trust, Gloucestershire Royal Hospital, Gloucester, UK; University Hospitals Birmingham NHS Foundation Trust, Queen Elizabeth Hospital Birmingham, Edgbaston, Birmingham, UK; Institute of Microbiology and Infection, The University of Birmingham, Edgbaston, Birmingham, UK. Electronic address: mark.garvey@uhb.nhs.uk.