1. School of Public Health, Zunyi Medical University, Zunyi, Guizhou Province 563000, China
2. Key Laboratory of Maternal & Child Health and Exposure Science of Guizhou Higher Education Institutes, Zunyi, Guizhou Province, 563000, China
3. Laboratory of Microbiology and Immunology, School of Basic Medical Sciences, Zunyi Medical University, No. 6 Xuefu Xilu, Zunyi 563006, PR China