[1] Freiburg Univ Hosp, Inst Environm Med & Hosp Epidemiol, D-79106 Freiburg, Germany
[2] Freiburg Univ Hosp, Dept Dermatol, D-79106 Freiburg, Germany
[3] Free Univ Berlin, Inst Hyg, D-1000 Berlin, Germany
[4] Natl Reference Ctr Surveillance Nosocomial Infect, Berlin, Germany