1. Department of Infectious Diseases, Keio University School of Medicine, Japan
2. Division of Infectious Diseases and Infection Control, Keio University Hospital, Japan
3. Department of Neurosurgery, Keio University School of Medicine, Japan
4. Division of Gastroenterology, Department of Internal Medicine, Keio University School of Medicine, Japan
5. Division of Hematology, Department of Internal Medicine, Keio University School of Medicine, Japan