1. Department of Clinical Microbiology and Immunology, Örebro Medical Center Hospital, SE-701 85Örebro,1 and
2. Servicio de Bacteriologı́ca, Centro Nacional de Microbiologı́ca, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain2
3. Department of Pharmaceutical Bioscience, Biomedical Centre, Uppsala University, SE-751 23 Uppsala,3 Sweden, and