[1] Shanxi Med Univ, Sch Clin Med 1, Taiyuan, Shanxi, Peoples R China
[2] Shanxi Prov Peoples Hosp, Dept Oral Med, Taiyuan, Shanxi, Peoples R China
[3] Shanxi Prov Peoples Hosp, Dept Hosp Infect Control, Taiyuan, Shanxi, Peoples R China
[4] Shanxi Med Univ, Clin Hosp 1, Dept Gastroenterol & Hepatol, Mailbox 427,85 Jiefang South Rd, Taiyuan 030001, Shanxi, Peoples R China