1. Department of Pediatrics, CHUV, CH-1011 Lausanne, Switzerland
2. Department of Fundamental Microbiology, University of Lausanne, Biophore Building, CH-1015 Lausanne, Switzerland
3. Institute of Microbiology, CHUV, CH-1011 Lausanne, Switzerland
4. Division of Clinical Pharmacology, CHUV, CH-1011 Lausanne, Switzerland
5. Department of Hospital Hygiene, CHUV, CH-1011 Lausanne, Switzerland
6. Laboratoire d'Antibiologie (UPRES EA-1156), Medicine School, F-44035 Nantes Cedex 01, France