1. Department of Pathology and Microbiology, Division of Microbiology, Nihon University School of Medicine, Tokyo, Japan.
2. Department of Otolaryngology Head and Neck Surgery, Division of Oral Surgery, Nihon University School of Medicine.
3. Department of Microbiology, Nihon University School of Dentistry, Tokyo, Japan.
4. Department of Pathology and Microbiology, Division of Pathology, Nihon University School of Medicine.