1. Department of Microbiology, School of Pharmaceutical Sciences; University of Shizuoka; Shizuoka Shizuoka 422 Japan
2. Max von Pettenkofer Institut für Hygiene und Medizische Mikrobiologie der Universität Munchen; Pettenkoferstrasse 9a; W 8000 Munich 2 Germany
3. Department of Bacteriology; National Institute of Health; shinjuku-ku Tokyo 162 Japan
4. Department of Epidemiology; Hokkaido Institute of Public Health; Sapporo Hokkaido 060 Japan
5. Department of Infectious Disease; Nagano Research Institute for Health and Pollution; Nagano Nagano 380 Japan
6. Department of Public Health; Aomori Prefectural Institute of Public Health and Environment; Aomori Aomori 030 Japan
7. Department of Public Health, School of Dentistry; Health Science University of Hokkaido; Tobetsu Hokkaido 069 Japan
8. Division of Animal Experimentation; Sapporo Medical College; Sapporo Hokkaido 060 Japan
9. Department of Microbiology, Medical School; University of Minnesota; Minneapolis MN 55455 U.S.A.