1. Department of General Medicine, Okayama University Graduate School of Medicine , Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558 , Japan
2. Department of Infectious Diseases, Okayama University Hospital , 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558 , Japan