我们研究发现肠道固有多枝梭菌可通过产生有机酸发挥抗EHEC感染的作用，但其作用机制尚不清楚。本项目拟在建立细胞感染模型和无菌小鼠感染模型的基础上，利用高效液相色谱和细菌计数等技术，分析多枝梭菌产生的主要有机酸及其对EHEC生长和毒素分泌的影响，探讨不同有机酸在抗EHEC感染中的作用；利用RT-qPCR、western blotting和电子显微镜等技术，研究多枝梭菌产生的主要有机酸对EHEC菌体结构及其致病因子的影响，探讨不同有机酸抗EHEC感染的直接作用分子机制；利用细胞跨膜电阻测定、荧光素标记葡聚糖示踪、流式细胞等技术，研究多枝梭菌产生的主要有机酸对肠道粘膜完整性和细胞功能的保护作用，探讨不同有机酸抗EHEC感染的间接作用分子机制。本课题的开展将不但为多枝梭菌抗EHEC感染的分子机制研究奠定基础，而且为今后临床应用多枝梭菌预防EHEC感染提供有力的科学依据，具有重要的理论和应用价值。

Our previous studies found that gut commensal bacteria Clostridium ramosum could protect from enterohemorrhage Escherichia coli (EHEC) infection through the production of organic acid. In order to explain this mechanism, cell infection model and germ free mouse infection model were established in this project. We used high performance liquid chromatography and bacterial counting, to analyze the main organic acids produced by Clostridium ramosum and its effect on the growth of EHEC and the secretion of shiga toxin; we used RT-qPCR, western blotting, electron microscopy, to analyze the effects of organic acids produced by Clostridium ramosum on EHEC cell structure and its virulence factors; we used transepithelial electrical resistance assay, fluorescein isothiocyanate labeled dextrans tracer, flow cytometry, to analyze the protective effects of organic acids produced by Clostridium ramosum on intestinal mucosal integrity and cell function. This study provides a basis molecular mechanism of the effect of Clostridium ramosum against EHEC infection, and provides a scientific basis for the clinical application of Clostridium ramosum to prevent EHEC infection in the future.