1. Department of Bacteriology; Okayama University Medical School; Okayama Okayama 700 Japan
2. Department of Microbiology; Sapporo Medical University; Sapporo Hokkaido 060 Japan
3. Laboratory of Biochemistry, Division of Ecological Sciences, Graduate School of Environmental Earth Science; Hokkaido University; Sapporo Hokkaido 060 Japan
4. Department of Preventive Dentistry, School of Dentistry; Health Sciences University of Hokkaido; Hokkaido 061-21 Japan
5. Departemnt of Ophthalmology, School of Medicine; Hokkaido University; Sapporo Hokkaido 061-21 Japan