Corresponding Author: Kenichi Imai

Department of Microbiology, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310 (Japan)
Tel. +81-3-3219-8115, Fax +81-3-3219-8317, E-Mail imai.kenichi@nihon-u.ac.jp