1. Division of Infectious Diseases, Department of Internal Medicine I, German Center for Infection Research, University of Tübingen, Otfried Müller Straße 12, 72074 Tübingen, Germany
2. Division of Infectious Diseases, Department of Diagnostic and Public Health, G. B. Rossi University Hospital, University of Verona, P.le L.A. Scuro 10, 37100 Verona, Italy