1. Department of Microbiology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki-shi, Osaka 569-8686, Japan 2Department of Nursing, Kobe Tokiwa College, Ohtani-cho 2-6-2, Nagata-ku, Kobe, Hyogo 653-0838, Japan 3VA Greater Los Angeles Healthcare System and Department of Physiology and Medicine, University of California at Los Angeles, CA, USA