[1] Tokyo Metropolitan Otsuka Hosp, Dept Pediat, Toshima Ku, Tokyo 1708476, Japan
[2] Keio Univ, Sch Med, Dept Pediat, Tokyo, Japan
[3] Tokyo Metropolitan Inst Publ Hlth, Dept Microbiol, Tokyo 1690073, Japan
[4] Keio Univ, Sch Med, Clin Res Ctr, Tokyo, Japan