1. Institute of Medical Microbiology Jinan University Guangzhou 510632 P. R. China
2. Foshan Institute of Medical Microbiology Foshan 528315 P. R. China
3. Department of Cardiovascular Surgery Union Hospital Tongji Medical College Huazhong University of Science and Technology Wuhan 430022 P. R. China
4. Department of Microbiology and Immunology College of Basic Medicine and Public Hygiene Jinan University Guangzhou 510632 P. R. China