1. Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, Tokyo
2. Department of Pediatrics, Saitama Medical School, Saitama
3. Sapporo Tetsudo Hospital, Hokkaido
4. Kanagawa Prefectural Institute of Public Health, Kanagawa
5. Department of Pediatrics, Chigasaki Municipal Hospital, Kanagawa, Japan