1. Division of Microbiology, National Institute of Health Sciences, 1–18–1 Kamiyoga, Setagaya-ku, Tokyo 158–8501, Japan
2. Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113–8657, Japan
3. Department of Oceanography, Tokai University, 3–20–1 Orido, Shimizu-ku, Shizuoka 424–8610, Japan
4. Tokai University Junior College, 101 Miyamae-cho, Aoi-ku, Shizuoka 420–8511, Japan
5. Shizuoka Institute of Environment and Hygiene, 4–27–2 Kita-Ando, Aoi-ku, Shizuoka 420–8637, Japan
6. Chubu Food and Environmental Safety Center, 663–3 Shima, Shimada, Shizuoka 428–0007, Japan