1. National Center for Hospital Hygiene, Frederiksberg Hospital, Copenhagen, Denmark
2. Department of Biostatistics, Statens Seruminstitut, Frederiksberg Hospital, Copenhagen, Denmark
3. Department of Clinical Microbiology, Frederiksberg Hospital, Copenhagen, Denmark
4. Department of Orthopaedic Surgery, Frederiksberg Hospital, Copenhagen, Denmark
5. Department of General Surgery, Frederiksberg Hospital, Copenhagen, Denmark
6. Electronic Dataprocessing Department, Frederiksberg Hospital, Copenhagen, Denmark