1. Department of Microbiology, School of Medicine; University of Occupational and Environmental Health; Kitakyushu Fukuoka 807 Japan
2. Department of Pathology, Faculty of Medicine; Prince of Songkla University; Songkla 90112 Thailand
3. Department of Clinical Laboratory; Takinomiya General Hospital; Kagawa 761-23 Japan
4. Department of Bacteriology; Osaka City University Medical School; Osaka Osaka 545 Japan