1. Department of Microbiology; Tokyo Metropolitan Research Laboratory of Public Health; Shinjuku-ku Tokyo 169 Japan
2. Division of Pediatrics; Urawa City Hospital; Urawa Saitama 336 Japan
3. Department of Pediatrics, School of Medicine; Keio University; Shinjuku-ku Tokyo 160 Japan
4. Department of Laboratory; Byotai-Seiri Clinical Laboratory; Itabashi-ku Tokyo 173 Japan