1. Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan
2. Division of Endoscopy, Hirosaki University Hospital, Hirosaki 036-8563, Japan
3. Division of Gastroenterology and Hematology, Hirosaki National Hospital, National Hospital Organization, Hirosaki 036-8545, Japan
4. Shibata Irika Co., Ltd., Hirosaki 036-8084, Japan
5. Department of Microbiology and Immunology, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan