[1] Osaka Univ, Res Inst Microbial Dis, Dept Bacterial Infect, Suita, Osaka 5650871, Japan
[2] Osaka Univ, Res Inst Microbial Dis, Dept Bacterial Toxinol, Suita, Osaka 5650871, Japan
[3] Kitasato Univ, Sch Vet Med & Anim Sci, Dept Vet Publ Hlth, Aomori 0348626, Japan