耐碳青霉烯类弗劳地柠檬酸杆菌的耐药基因及分子分型

Antimicrobial resistance genes and molecular typing of carbapenem-resis-tant Citrobacter freundii

摘要:

目的 分析耐碳青霉烯类弗劳地柠檬酸杆菌(CRCF)的检出率、分布特点、耐药机制及分子分型,为临床治疗与防控提供理论依据。方法 分析2020—2023年福建医科大学附属泉州第一医院分离CRCF的药敏结果,验证菌株耐药表型,扩增耐药基因,多位点序列分型(MLST)分析菌株同源性,全基因组测序分析同时携带bla_VIM-1、bla_NDM-1的CF17菌株。结果 共检出非重复弗劳地柠檬酸杆菌119株,其中CRCF 27株,占22.7%。CRCF主要分离自神经外科和泌尿外科,标本类型主要是中段尿;对碳青霉烯类和头孢菌素均耐药,对阿米卡星的耐药率较低,对替加环素及多黏菌素均敏感,对其余抗菌药物的耐药率>50%。成功复苏的22株CRCF耐药表型均阳性, 均携带耐药基因,其中17株(77.3%)携带单耐药基因,包括14株bla_NDM-1,2株bla_KPC-2,1株bla_NDM-5;5株(22.7%) 同时携带双耐药基因,包括同时携带bla_KPC-2、bla_NDM-1(共3株),同时携带bla_NDM-1、bla_IMP和同时携带bla_VIM-1、bla_NDM-1(各1株);共检出8个ST型,ST116、ST532分别有8、6株。CF17为ST116,携带的bla_VIM-1、bla_NDM-1位于不同的质粒上,分别为IncA、IncX3。结论 CRCF以多重耐药为主,主要耐药机制是携带bla_NDM-1,部分菌株同时携带双耐药基因,以ST116和ST532为主,CF17是目前已知国内首次分离报告同时携带bla_VIM-1及bla_NDM-1耐药基因的弗劳地柠檬酸杆菌。

Abstract:

Objective To analyze the detection rate, distribution characteristics, resistance mechanism, and molecular typing of carbapenem-resistant Citrobacter freundii (CRCF), providing theoretical basis for clinical treatment and prevention. Methods Antimicrobial susceptibility testing results of CRCF isolated from Quanzhou First Hospital Affiliated to Fujian Medical University from 2020 to 2023 were analyzed. Resistance phenotypes of the strains were verified; resistance genes were amplified; strain homology was analyzed by multi-locus sequencing ty-ping (MLST). Whole genome sequencing analysis was performed on CF17 strains carrying both bla_VIM-1 and bla_NDM-1. Results A total of 119 strains of non-repetitive Citrobacter freundii were detected, 27 strains were CRCF, accounting for 22.7%. CRCF was mainly isolated from departments of neurosurgery and urology, and the specimen type was mainly midstream urine. Strains were resistant to both carbapenems and cephalosporins, less resistant to amikacin, susceptible to both tigecycline and polymyxin, and with a resistance rate of >50% to other antimicrobial agents. 22 CRCF strains were successfully recovered and all were positive for antimicrobial resistance phenotype and genes. 17 strains (77.3%) carried single resistance genes, including 14 strains carrying bla_NDM-1, 2 strains carrying bla_KPC-2, and 1 strain carrying bla_NDM-5. 5 strains (22.7%) carried dual antimicrobial resistance genes, including strains carrying both bla_KPC-2 and bla_NDM-1 (n=3), strain carrying both bla_NDM-1 and bla_IMP (n=1), and strain carrying both bla_VIM-1 and bla_NDM-1 (n=1). A total of 8 ST types were detected, with 8 and 6 strains being ST116 and ST532, respectively. CF17 was ST116, carrying bla_VIM-1 and bla_NDM-1 on different plasmids, namely IncA and IncX3, respectively. Conclusion CRCF strains are mostly multidrug-resistant, with the presence of bla_NDM-1 being the major resistance mechanism. Some strains also carry dual resistance genes, mainly ST116 and ST532. CF17 is currently the first isolated and reported Citrobacter freundii that carries both bla_VIM-1 and bla_NDM-1 resistance genes in China.