新现高致病性沙门菌血清型1,4,[5],12:i:-遗传特征和分子进化机制研究

新现高致病沙门菌血清型1,4,[5],12:i:-在全球暴发流行，其也是我国引起食源性疾病的主要血清型。研究显示1,4,[5],12:i:-是鼠伤寒单项菌变种，其第Ⅱ相鞭毛抗原表达相关fljBA操纵子基因发生不同程度缺失。这一非典型血清型的产生和流行体现了沙门菌进化的新机制。但目前1,4,[5],12:i:-在我国食品中的分布并不清楚，且尚未在全基因组层面上对其遗传特征和进化机制进行系统分析。本项目通过对1,4,[5],12:i:-鉴定、耐药性分析和分子分型，确定其在我国食品中的分布规律和遗传特征；并从全基因组层面上研究1,4,[5],12:i:-的系统发生关系、群体遗传结构和进化选择压力，及其第Ⅱ相鞭毛抗原缺失方式，在此基础上，明确1,4,[5],12:i:-血清型遗传变异规律，探索其产生的机制和进化的背后推动力。为制定预防和控制沙门菌的新策略，保障食品安全提供理论基础。

Salmonella enterica subsp. enterica serovar 1,4,[5],12:i:- is a monophasic variant of Salmonella Typhimurium, which has recently been recognized as an emerging cause of infection worldwide. This bacterium has also ranked among the most frequent serovars causing human salmonellosis in China. However, there are no reports on its distribution in Chinese food and its molecular characteristics and evolutionary mechanism. Serotyping, polymerase chain reaction, antibiotic resistance, and molecular subtyping assays were used to investigate the prevalence and genotypic diversity of this serological variant in food products in China. Based on the full length of genome sequences from Salmonella 1,4,[5],12:i:- isolated from Chinese food, we will analyze the phylogenetic realationship, population genetic structure, selective pressure and study the evolutionary mechanism of Salmonella 1,4,[5],12:i:- isolates. This study is useful in understanding the prevalence and evolution of Salmonella 1,4,[5],12:i:-，and provides an important theoretical basis for food safety in prevention and control of Salmonella in the future.