1. School of Pure and Applied Biology, University of Wales College of Cardiff, Cardiff CF1 3TL,1
2. Department of Oral Microbiology, Niigata University School of Dentistry, Niigata 951, Japan2
3. Department of Oral Medicine, Pathology and Microbiology, Centre for the Study of Oral Disease, Bristol Dental Hospital and School, Bristol BS1 2LY,3 and
4. Department of Oral Medicine and Pathology, Guys and St. Thomas’s Medical and Dental School, Guy’s Hospital, London SE1 9RT,4United Kingdom, and