1. Laboratory for Pharmaceutical Microbiology, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium
2. Laboratory for Microbiology, Ghent University, Ledeganckstraat 35, B-9000 Ghent, Belgium
3. Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109-0646, USA
4. Cardiff School of Biosciences, PO Box 915, Cardiff University, Cardiff CF10 3TL, UK