1. Department of Microbiology, Gachon Medical School, Incheon, Korea.
2. Department of Occupational Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Microbiology, College of Medicine, Ewha Womans University, Seoul, Korea.