This work was supported by the Japanese Society for the Promotion of Science KAKENHI, Grant No. 24590846, and was also supported in part by a grant from the Ministry of Health Labour and Welfare of Japan (H24-Shinko-Ippan-005) and the Daido Life Welfare Foundation, Osaka, Japan. We are grateful to Dr. Hirata, Dr. Chijiwa, Mr. Kimoto, Ms. Uemura and Dr. Saeki, of the Fukuoka Institute of Health and Environmental Sciences, for their invaluable advice. The MLST data are publicly available at http://www2.warwick.ac.uk/mlst, which is currently supported by a grant from the Biotechnology and Biological Sciences Research Council.