1. Institute of Hygiene and Occupational Medicine, University Hospital Essen, University of Duisburg–Essen (Germany), Virchowstraße 171, D-45147 Essen, Germany
2. Institute of Medical Microbiology, University Hospital Essen, University of Duisburg–Essen (Germany), Virchowstraße 174, D-45147 Essen, Germany
3. Clinic of Urology, University Hospital Essen, University of Duisburg–Essen (Germany), Hufelandstraße 22, D-45122 Essen, Germany