2017年至2020年临床分离mcr-1阳性多黏菌素耐药大肠埃希菌流行病学特征

Epidemiological characteristics of mcr-1-positive clinical Escherichia coli isolated from 2017 to 2020 in China

目的监测2017年至2020年临床分离得到大肠埃希菌中多黏菌素耐药mcr-1阳性菌株的分子流行病学特征。方法使用聚合酶链反应技术筛查mcr-1阳性菌株从临床分离的1518株大肠埃希菌。采用16SrRNA验证所有纳入分析的mcr-1阳性菌株的菌种。使用微量肉汤法与琼脂二倍稀释法进行抗菌药物敏感实验。所有mcr-1阳性菌株通过多位点序列分型(MLST)进行同源性分析。结果在1518株临床分离大肠埃希菌中,检测到14株(0.92%)携带mcr-1基因的大肠埃希菌。微量肉汤法显示14株mcr-1阳性菌株均对多黏菌素耐药。16SrRNA验证14株mcr-1阳性菌株类型均为大肠埃希菌。14株阳性菌株对临床常用抗菌药物中的第三、四代头孢菌素、单环β-内酰胺类以及喹诺酮类等都表现出较高的耐药率,尤其阳性菌株对头孢唑啉、头孢呋辛、头孢噻肟、头孢曲松、头孢他啶、头孢哌酮和头孢吡肟的耐药率在57.1%~92.9%,对氨曲南的耐药率为64.3%,对环丙沙星和左氧氟沙星的耐药率达到92.9%;14株mcr-1阳性菌对β内酰胺类酶抑制剂复合制剂和碳青霉烯类药物(亚胺培南、美罗培南和厄他培南)的耐药率较低,均为14.3%;14株mcr-1阳性菌对庆大霉素和阿米卡星的耐药率为57.1%和21.4%;对四环素和米诺环素耐药率分别为85.7%和64.3%,但是均对替加环素表现为敏感。MLST分析显示14株mcr-1阳性菌株分别获得14种不同STs分型。对14株阳性菌株进行聚类分析显示较为分散,相似度低于60%。结论临床分离的大肠杆菌mcr-1阳性菌株的检出率低于往年。14个不同的ST分型显示mcr-1阳性大肠埃希菌的遗传多样性。应进一步关注阳性菌株的多重耐药表型和传播。

Objective To monitor molecular epidemiological characteristics of mcr-1-positive strains in colistin resistant Escherichia coli(E.coli.)in 2017-2020.Methods mcr-1-positive isolates was screened by polymerase chain reaction(PCR)technology from clinical separation of 1518 E.coli.The mcr-1-positive isolates of all inclusion analysis were verified by 16 SrRNA.Antimicrobial susceptibility was determined by broth microdilution method and agar two-fold dilution.All mcr-1-positive strains analyzed by Multilocus Sequence Typing(MLST).Results Among 1518 strains of clinically isolated E.coli,14(0.92%)strains of E.coli carrying mcr-1 gene were detected.The resistance of 14 mcr-1-positive strains to colistin was determined by broth microdilution method.All mcr-1-positive strains were identified as E.coli by 16SrRNA.And 14 strains showed high resistance to cephalosporins,monocyclicβ-lactams and quinolones,especially to cefazolin,cefuroxime,cefotaxime,ceftriaxone,ceftazidime,cefoperazone and cefepime.The resistance rate to aztreonam was 64.3%;the resistance rate to ciprofloxacin and levofloxacin was 92.9%;the resistance rates of 14 mcr-1-positive bacteria toβ-lactamase inhibitors and carbapenem drugs(imipenem,meropenem and erapenem)were14.3%,and the resistance rates of 14 mcr-1-positive bacteria to gentamicin and amikacin were 57.1%and21.4%,respectively.The resistance rates to tetracycline and minocycline were 85.7%and 64.3%respectively,but were sensitive to tigecycline.And 14 different ST genotypes were obtained by MLST analysis of 14 mcr-1 positive strains.The clustering of 14 positive strains showed that the similarity coefficient was less than 60%.Conclusion The detection rate of E.coli mcr-1-positive strains isolated from clinic was less than that in previous years.And 14different ST revealed genetic diversity.Further attention should be given to the multidrug-resistance phenotype and transmission of positive strains.