Study of antimicrobial resistance in E. coli M19736 strain and evolved XDR-E. coli M19736. Escherichia coli strain:NEC-M19736

In the present study, we wonder about the ability of E. coli M19736 clinical strain belonging to sporadic clone ST615 that was one of the first isolates harboring the mcr-1 gene in Latin America , to adapt to XDR phenotype by conjugation and transformation assays. The conservation along time of ARG in evolved MDR and XDR-E. coli M19736 strains showed different patterns of maintenance as well as variability in the capacity to transfer in turn the acquired conjugative plasmids including co-transfer of different plasmids. In addition, we identified EV in the native and in the evolved XDR-E. coli M19736 strains with crucial content for the competence of Antimicrobial resistance in the nosocomial niche, including the blaCTX-M-15 gene though the pDCAG1-CTX-M-15 was previously lost. As a whole, this scenario reveals the relevant role of sporadic clones as common vectors for the dissemination of acquired antimicrobial resistance within the framework of the HGT processes.

本研究旨在探究属于散发克隆序列型615（ST615）的大肠杆菌（Escherichia coli）M19736临床菌株的适应能力——该菌株是拉丁美洲首批携带mcr-1基因的分离株之一——通过接合实验与转化实验适配广泛耐药（Extensively Drug-resistant，XDR）表型的能力。对进化后的多重耐药（Multidrug-resistant，MDR）与广泛耐药大肠杆菌M19736菌株中抗生素抗性基因（Antimicrobial Resistance Genes，ARG）的长期保留特征分析显示，其抗性基因的维持模式存在差异，且依次转移获得的接合性质粒（包括不同质粒的共转移）的能力亦存在变异。此外，我们在野生型及进化后的广泛耐药大肠杆菌M19736菌株中鉴定出了胞外囊泡（Extracellular Vesicles，EV），其携带的关键组分可增强细菌在医院生境中的抗生素抗性能力，其中包含blaCTX-M-15基因——尽管pDCAG1-CTX-M-15质粒此前已丢失。总体而言，该研究结果揭示了散发克隆作为水平基因转移（Horizontal Gene Transfer，HGT）框架下获得性抗生素抗性传播的常见载体的重要作用。