1. Microbial Function Laboratory, National Food Research Institute, 2‐1‐12 Kannondai, Tsukuba, Ibaraki 305‐8642, Japan.
2. Bacteriology Division, Osaka Prefectural Institute of Public Health, 1‐3‐69 Nakamichi, Higashinari‐ku, Osaka 537‐0025, Japan.
3. Department of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Kita 18, Nishi 9, Kita‐ku, Sapporo 060‐0818, Japan.
4. Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka 422‐8529, Japan.