1. Laboratorium voor Microbiologie, Universiteit Gent, K. L. Ledeganckstraat 35, B-9000 Ghent, Belgium
2. National Institute of Public Health and the Environment, Bilthoven, The Netherlands
3. Department of Medical Microbiology, University of Edinburgh, Edinburgh, UK
4. Department of Medical Microbiology, University Hospital UIA, Antwerp, Belgium