1. College of Animal Sciences and Veterinary Medicine, Guangxi University, Nanning, People's Republic of China.
2. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, People's Republic of China.
3. CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China.