产超广谱β-内酰胺酶(ESBL)大肠杆菌已成为一类广泛污染水源的耐药菌。我们前期工作已证实，水源产ESBL大肠杆菌会通过饮水途径在小鼠肠道内滞留且大量繁殖，并与肠道固有菌群之间发生了耐药质粒的水平转移。因此我们推测：当人和动物通过饮水摄入水源产ESBL大肠杆菌后，这些耐药菌株会与肠道固有菌群之间发生耐药质粒的水平转移，是造成ESBL耐药基因大面积散播的重要途径。为证实这一假说，我将通过抗性基因插入和双荧光标记技术构建水源产ESBL大肠杆菌耐药质粒水平转移的小鼠模型，探讨水源产ESBL大肠杆菌在小鼠肠道内的分布规律，明确肠道内接合子的种属和丰度，然后从质粒本身和肠道微环境等多个角度探讨饮用含有水源产ESBL大肠杆菌的水后，耐药质粒在小鼠肠道内水平转移规律及其分子机理。本课题将从新的视角阐明耐药基因水平转移的机制，为耐药性扩散的防控提供新的靶点和理论依据。

Accumulating evidence indicates that extended-spectrum beta-lactamase-producing (ESBL) Escherichia coli (E. coli) has become a frequently detected antibiotic resistance bacterium in water environments. Our previous studies showed that ESBL-producing E. coli in water environments can retain and multiply in mouse intestinal tract through drinking water route; more importantly, mouse intestinal flora can become recipient bacteria of the antibiotic resistant plasmid from water-borne ESBL-producing E. coli. Based on our previous research, we speculate that water-derived ESBL-producing E. coli can horizontally transfer antibiotic-resistant plasmid to animal or human intestinal flora, therefore triggering extensive dissemination of antibiotic-resistant gene. To confirm this hypothesis, we will develop a mouse model of antibiotic resistance plasmid horizontal transfer through antibiotic resistance gene insertion and dual fluorescence labeling techniques, and further make clear distribution characterization of water-derived ESBL-producing E. coli in mouse intestinal tract, and elucidate the abundance and species of transconjugants in mouse digestive tract. Based on the experiment above, both plasmid and intestinal niche will be analyzed to explore horizontal transfer mechanism of antibiotic resistance plasmid of water-derived ESBL-producing E. coli in mouse intestinal tract via drinking water route. This proposal will clarify the molecular mechanism of water-derived antibiotic resistance gene horizontal transfer in human or animal intestinal tract from a new perspective, and provide new targets and theoretical basis for the prevention and control of antibiotic resistance genes diffusion.