沙门菌是世界上食源性腹泻最常见的病原菌之一，其对公共卫生安全构成了重大威胁。硫化氢表型一直是沙门菌初筛和鉴定的重要生化指标。但是，近几年国内外硫化氢阴性罕见沙门菌相关的研究报道不断出现。本课题组亦发现其在我国的流行有上升趋势，并首次发现了一簇属于新序列型ST1751的硫化氢阴性山夫登堡沙门菌在上海地区的流行。沙门菌这种新的流行变异趋势及其对食品安全和公共健康的潜在威胁不容忽视。本项目拟在前期工作基础上，深入系统地开展硫化氢阴性沙门菌在我国的流行特征与变异变迁规律研究；通过代表性菌株的全基因组测序及生物信息学分析，挖掘基因组结构变异、基因水平转移、基因重组等变异事件，探究基因变异事件与表型和功能的关联，从而揭示硫化氢阴性沙门菌变异流行的分子机制；通过系统发生分析与种群结构重建，阐明我国硫化氢阴性沙门菌的传播演化规律，及其与阳性菌的亲缘进化关系，为我国沙门菌病的防控提供科学依据。

Salmonella enterica, the causative agent of Salmonellosis, is one of the most common pathogenic bacteria causing food-borne diarrhea worldwide, posing a serious threat to public health. In recent years, the H2S-negative atypical Salmonella enterica emerged worldwide. Notably, we also found the emergence and prevalence of the H2S-negative Salmonella in China, and identified a unique cluster of the H2S-negative Salmonella senftenberg belonging to a new sequence type ST1751, which has emerged and circulated in Shanghai City. So the potential threat to food safety and public health from the epideminc and variation trend of the H2S-negative atypical Salmonella in Mainland China should not be underestimated. Here we will conduct the study on the epidemiological characteristics and changing trend of the H2S-negative Salmonella in Mainland China. Furthermore, we will select the representative strains of the H2S-negative Salmonella and submit for whole genome sequencing to clarify the molecular mechanism of emergence and prevalence of the H2S-negative Salmonella, and to investigate the role of recombination, insertion/deletion, and horizontal gene transfer in the variation and evolution of the H2S-negative Salmonella. Additionally, phylogenetic analysis based on single-nucleotide polymorphisms and core-pan genome was performed to elucidate the evolution and dissemination of the H2S-negative Salmonella in China. In conclusion, this study can provide the scientific basis for the salmonellosis surveillance, early warning and confirmation of the outbreak, source-tracking, transmission survey, and formulation of the control and prevention strategies.