1. Department of Gastroenterology, Xiangya Hospital of Central South University, Changsha 410008, China
2. Department of Microbiology, School of Basic Medical Science, Central South University, Changsha 410078, China
3. Department of Parasitology, School of Basic Medical Science, Central South University, Changsha 410078, China
4. National Clinical Research Center for Geriatric Disorders, Xiangya Hospital of Central South University, Changsha 410008, China