1. Department of Infectious Diseases, The University of Tokyo Hospital
2. Department of Infectious Diseases, Tokyo Medical Dental University Hospital
3. Department of Pediatric Surgery, The University of Tokyo Hospital
4. Department of Infection Control and Prevention, The University of Tokyo Hospital, Bunkyo City, Tokyo, Japan
5. Yakult Central Institute, Yakult Honsha Co., Ltd, Kunitachi City, Tokyo, Japan.