1. Department of Critical Care Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Department of Surgery, Soonchunhyang University Bucheon Hospital, Bucheon, Korea.
4. Department of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
5. Infection Control Office, Samsung Medical Center, Seoul, Korea.