[Antimicrobial resistance and plasmid-mediated colistin resistance mechanism of diarrheagenic Escherichia coli recovered from foods in parts of China in 2020].

Objective: To investigate the antimicrobial resistance of food-borne diarrheagenic Escherichia coli (DEC) and the prevalence of mcr genes that mediates mobile colistin resistance in parts of China, 2020. Methods: For 91 DEC isolates recovered from food sources collected from Fujian province, Hebei province, Inner Mongolia Autonomous Region and Shanghai city in 2020, Vitek2 Compact biochemical identification and antimicrobial susceptibility testing platform was used for the detection of antimicrobial susceptibility testing (AST) against to 18 kinds of antimicrobial compounds belonging to 9 categories, and multi-polymerase chain reaction (mPCR) was used to detect the mcr-1-mcr-9 genes, then a further AST, whole genome sequencing (WGS) and bioinformatics analysis were platformed for these DEC isolates which were PCR positive for mcr genes. Results: Seventy in 91 isolates showed different antimicrobial resistance levels to the drugs tested with a resistance rate of 76.92%. The isolates showed the highest antimicrobial resistance rates to ampicillin (69.23%, 63/91) and trimethoprim-sulfamethoxazole (59.34%, 54/91), respectively. The multiple drug-resistant rate was 47.25% (43/91). Two mcr-1 gene and ESBL (extended-spectrum beta-lactamase) positive EAEC (enteroaggregative Escherichia coli) strains were detected. One of them was identified as serotype of O11:H6, which showed a resistance profile to 25 tested drugs referring to 10 classes, and 38 drug resistance genes were predicted by genome analysis. The other one was O16:H48 serotype, which was resistant to 21 tested drugs belonging to 7 classes and carried a new variant of mcr-1 gene (mcr-1.35). Conclusion: An overall high-level antimicrobial resistance was found among foodborne DEC isolates recovered from parts of China in 2020, and so was the MDR (multi-drug resistance) condition. MDR strains carrying multiple resistance genes such as mcr-1 gene were detected, and a new variant of mcr-1 gene was also found. It is necessary to continue with a dynamic monitoring on DEC contamination and an ongoing research into antimicrobial resistance mechanisms.目的： 探讨我国部分地区2020年食源性致泻大肠埃希菌（diarrheagenic Escherichia coli，DEC）的耐药性以及质粒介导黏菌素耐药基因mcr的携带情况。 方法： 针对我国福建省、河北省、内蒙古自治区和上海市等地区2020年度食品中分离获得的91株致泻大肠埃希菌，采用Vitek2 Compact生化鉴定和药敏检测平台测定其对9类18种抗菌药物的敏感性，采用多重聚合酶链式反应（mPCR）检测mcr-1~mcr-9基因的携带情况，并对mcr基因PCR阳性菌株开展进一步药敏实验、全基因组测序和生物信息学分析。 结果： 91株致泻大肠埃希菌总体耐药率为76.92%（70/91），对氨苄西林和甲氧苄啶-磺胺甲噁唑的耐药率最高，分别为69.23%（63/91）、59.34%（54/91），多重耐药菌株占47.25%（43/91）；检出2株mcr-1基因和ESBL（extended-spectrum beta-lactamase，超广谱β内酰胺酶）均为阳性的EAEC（enteroaggregative Escherichia coli，肠道集聚性大肠埃希菌）菌株，其中1株为O11：H6血清型，可对10类25种测试药物耐药且基因组预测出38种耐药基因，另1株为O16：H48血清型，可对7类21种测试药物耐药，并携带mcr-1基因新变体mcr-1.35。 结论： 2020年我国部分地区食源性致泻大肠埃希菌分离株的整体耐药水平较高，多重耐药情况严重，检出携带mcr-1基因等多种耐药基因的多重耐药菌株，且发现mcr-1基因新变体，需继续开展动态污染和耐药监测并持续开展耐药机制研究。.