1. Department of Family Medicine, Inje University Haeundae Paik Hospital, Busan, Korea.
2. Office of Hospital Infection Control, Chonnam National University, Gwangju, Korea.
3. Department of Internal Medicine, Chonnam National University, Gwangju, Korea.
4. Office of Hospital Infection Control, Korea University Anam Hospital, Seoul, Korea.
5. Department of Internal Medicine, Korea University Anam Hospital, Seoul, Korea.
6. Office of Hospital Infection Control, Hanyang University Seoul Hospital, Seoul, Korea.
7. Department of Internal Medicine, Hanyang University Seoul Hospital, Seoul, Korea.