1. Laboratory of Microbiology, School of Health Sciences, Faculty of Medicine, University of the Ryukyus , 207 Uehara, Nishihara-cho, Okinawa 903-0215 , Japan
2. Department of Clinical Laboratory, Urasoe General Hospital , 4-16-1 Iso, Urasoe-shi, Okinawa 901-2132 , Japan