1. Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway
2. Department of Microbiology, Forsyth Institute, Cambridge, MA, USA
3. Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
4. Department of Periodontics and Dental Hygiene, School of Dentistry, University of Texas Health Science Center at Houston, Houston, TX, USA