山东省聊城地区耐碳青酶烯类肠杆菌目细菌黏菌素耐药基因mcr-1相关感染的分子机制及临床特征

Molecular mechanism and clinical characteristics of colistin resistance gene mcr-1 in Carbapenem-resistant Enterobacteriaceae from Liaocheng area,Shandong Province

目的 探讨携带mcr-1耐药基因的耐碳青酶烯类肠杆菌目细菌(CRE)相关感染的分子机制及临床特征,为该类菌株感染的临床诊疗及预防区域内传播与暴发流行提供参考依据。方法 收集聊城市第二人民医院2016年1月—2022年12月分离自临床的非重复CRE,采用乙二胺四乙酸碳青霉烯酶失活试验(eCIM)与改良碳青霉烯酶失活试验(mCIM)检测碳青霉烯酶表型;采用微量肉汤稀释法进行体外药敏试验;采用聚合酶链反应(PCR)扩增并测序分析与黏菌素耐药相关的mcr-1基因及碳青霉烯类耐药基因;采用多位点序列分型技术(MLST)确定菌株的序列分型(ST)。收集mcr-1基因阳性菌株感染患者的病历资料,统计相关信息并进行分析。结果 共分离CRE菌株127株,包括65株大肠埃希菌,52株肺炎克雷伯菌,3株阴沟肠杆菌,3株产酸克雷伯菌,2株奇异变形杆菌,以及产气肠杆菌、弗氏柠檬酸杆菌各1株。所有CRE菌株中有6株携带mcr-1基因,且同时为blaNDM-5基因阳性。携带mcr-1的6株CRE仅对替加环素具有较高的敏感性,表现为低水平耐药。MLST分型结果显示有4种不同的ST型别,其中2株为ST167,2株为ST410,其余2株分别株为ST48和ST361。6例患者的性别、年龄、抗菌药物使用史、基础疾病及病情严重程度均不同,各项感染指标有不同程度的升高,患者最终均治愈出院。结论 黏菌素耐药基因mcr-1在聊城地区临床分离的CRE中检出率较低且呈低水平耐药,但已发现该基因与碳青霉烯酶耐药基因共存的现象,需引起临床重视并加强监测。

Objective To explore the molecular mechanism and clinical characteristics of Carbapenem-resistant Enterobacteriaceae(CRE)-related infections carrying colistin-resistance gene mcr-1,and to provide a reference basis for the clinical diagnosis and treatment of infections with such strains as well as for the prevention of spread of outbreaks and epidemics in the region.Methods Non-repetitive CRE were collected from clinical isolates in the Second People's Hospital of Liaocheng from January 2016 to December 2022,and the carbapenemase phenotype was detected using modified carbapenemase inactivation test(mCIM)combined with ethylenediamine tetra-acetic acid carbapenemase inactivation test(eCIM).The microbroth dilution method or agar dilution method were used for in vitro drug susceptibility test,polymerase chain reaction(PCR)was used to detect mcr-1 gene associated with colistin resistance and Carbapenem resistance genes.The multilocus sequence typing(MLST)technique was used to determine the sequence typing(ST)of strains.Case data of patients infected with mcr-1-positive strains were collected,and the relevant information was statistically analyzed.Results A total of 127 CRE strains were isolated,including 65 strains of Escherichia coli,52 strains of Klebsiella pneumoniae,3 strains of Enterobacter cloacae,3 strains of Klebsiella acidogenes,2 strains of Proteus mirabilis,1 strain of Citrobacter freundii and 1 strain of Enterobacter aerogenes;among which 6 strains carried the colistin-resistant gene mcr-1 and were also blaNDM-5 gene positive.The 6 strains of CRE carrying mcr-1 were only highly susceptible to Tigecycline,which demonstrated a low level of resistance.The results of MLST typing showed that there were four different ST phenotypes,2 strains of which were ST167,2 strains were ST410,and the remaining two strains were ST48 and ST361,respectively.The 6 patients were with different genders,ages,underlying diseases,antibiotic history and severity of illness,with different degrees of elevation of various infection indexes,and they were all finally cured and discharged from the hospital.Conclusions The detectable rate of colistin resistance gene mcr-1 was low in the clinical isolates of CRE in Liaocheng area,and the drug resistance was low,but the coexistence of mcr-1 and carbapenemase resistance genes was found,suggesting that clinical attention should be paid and its monitoring should be strengthened.