1. 1Division of Microbiology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501, Japan
2. 2Saitama Institute of Public Health, Saitama 338-0824, Japan
3. 3Department of Microbiology, Kanagawa Institute of Public Health, Simomachiya, Chigawaki 253-0087, Japan
4. 4Department of Medical Technology, Hirosaki University School of Sciences, Honcho 66-1, Hirosaki 036-8564, Japan