[1] Univ Aberdeen, Sect Populat Hlth, Sch Med, Aberdeen AB25 2ZD, Scotland
[2] Aberdeen Royal Infirm, Aberdeen AB25 2ZN, Scotland
[3] Hlth Protect Agcy, Lab Healthcare Associated Infect, Ctr Infect, London, England
[4] Univ Oxford Wolfson Coll, Ctr Stat Med, Oxford OX2 6UD, England
[5] Radboud Univ Nijmegen, Gen Internal Med, Med Ctr, NL-6525 ED Nijmegen, Netherlands
[6] St Elisabeth Univ, Dept Oncol, St Elisabeth Canc Inst, Coll Hlth Sci, Bratislava, Slovakia