1. Department of Pathological and Bacterial Laboratory; Toranomon Hospital; Minato-ku Tokyo 105-8470 Japan
2. Department of Bacteriology; National Institute of Infectious Diseases; Shinjuku-ku Tokyo 162-8640 Japan
3. Department of Gastroenterology, Toranomon Hospital; Tokyo Women's Medical College; Shinjuku-ku Tokyo 162-8666 Japan
4. Institute of Geriatrics; Tokyo Women's Medical College; Shinjuku-ku Tokyo 162-8666 Japan