1. Division of Oral Molecular Microbiology, Department of Oral Pathobiological Science; Hokkaido University Graduate School of Dental Medicine; Sapporo 060-8586 Japan
2. Department of Molecular Bacteriology and Immunology, Graduate School of Medicine; University of the Ryukyus; Okinawa 903-0125 Japan
3. Department of Bacterial Infection and Host Response, Graduate School of Medical and Dental Sciences; Tokyo Medical and Dental University; Tokyo Japan
4. Department of Oral Microbiology, School of Dentistry; Health Sciences University of Hokkaido; Ishikari Hokkaido 061-0293 Japan