山梨糖代谢增强MCR-1阳性大肠杆菌适应性及致病性的机制研究

多粘菌素是临床治疗重症感染“最后一线”药物，而MCR-1是首次报道的质粒介导多粘菌素耐药基因，MCR-1的出现给临床治疗带来严峻挑战。申请人前期发现：①MCR-1阳性大肠杆菌（MCREC）临床定植率很高且易形成多重耐药引起严重感染（CID 2018, AAC 2017）；②与其它来源比，感染源MCREC中山梨糖代谢通路富集（Lancet Microbe 2020）。本项目预实验显示：在营养缺陷环境下有山梨糖操纵子MCREC生长能力显著高于无山梨糖操纵子的细菌，且其大蜡螟致死率更高，提示MCREC可能利用山梨糖代谢增强细菌适应性及致病性。本项目拟采用代谢组学等方法找到MCREC利用山梨糖代谢增强细菌适应性及致病性的关键代谢物及代谢通路；采用基因敲除、代谢回补和动物模型等方法验证关键代谢通路参与调节山梨糖介导MCREC适应性及致病性增强的分子机制，为临床MCREC感染防控和治疗提供新思路。

Colistin was recognized as the last resort antimicrobial agent to defense against infections caused by multi-drug resistant bacteria. The emergence of the plasmid-borne mobile colistin resistance gene, MCR-1, brings severe challenges to clinic. And previous researches observed that MCR-1-positive Escherichia coli (MCREC) has a high clinical colonization rate and MCR-1 is easy to coexist with other important antibiotic resistance genes and become multi-drug resistance（CID 2018, AAC 2017）. And we also found that compared with other samples, the sorbose metabolism pathway is enriched in MCRPEC isolated from the infectious (Lancet Microbe 2020). Our further experiments showed that the growth adaptability of MCREC with the sorbose operon is significantly higher than that without sorbose operon in the nutrient deficient environment. The fatality rate of wax moth infected with MCREC with the sorbose operon is higher, suggesting that MCREC may use sorbose metabolism to enhance bacterial adaptability and pathogenicity. In this research, we intend to use metabolomics, transmission electron microscopy, and mouse models to clarify the key metabolic pathway and the specific mechanism of MCRPEC using sorbose metabolism to enhance adaptability and pathogenicity. Furthermore, gene knockout, metabolic replenishment, and animal models are used to verify the key metabolic pathway involved in regulating sorbitose-mediated MCREC adaptability and pathogenicity. This study aims to provide theoretical support for the clinical prevention and control of MCR-1.