1. Department of Medicine and Therapeutics, Control and Prevention of Infectious Diseases, Faculty of Medicine; University of the Ryukyus; Okinawa 903-0215 Japan
2. Department of Infection Control and Laboratory Diagnostics, Internal Medicine; Tohoku University Graduate School of Medicine; Sendai Miyagi 980-8575 Japan
3. Microbiology and Immunology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine; Tohoku University; Sendai Miyagi 980-8575 Japan
4. Infection-Control Research Center; Tohoku University Hospital; Sendai Miyagi 980-8575 Japan