1. Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan 2Department of Bacteriology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku Tokyo 113-8421, Japan 3Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University, 50 Ilwon-dong, Kangnam-ku Seoul 135-710, Korea