1. Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, the Netherlands
2. Department of Clinical Microbiology, Hvidovre University Hospital, Hvidovre, Denmark
3. Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
4. Institute of Hygiene, University of Münster, Münster, Germany
5. Department of Microbiology and Infection Prevention, Atrium-Orbis Medical Center, Sittard, the Netherlands
6. Department of Mathematics and Statistics, University of Helsinki, Helsinki, Finland
7. Department for Periodontology, University of Münster, Münster, Germany