两株携带bla_(NDM)基因肠杆菌目细菌的分子流行病学特征研究

Molecular Epidemiological Characterization of Two Strains of bla_(NDM)-positive Enterobacteriaceae

目的:了解平顶山某医院两株携带bla_(NDM)基因肠杆菌目细菌临床分离株的分子流行病学特征,为该类病原菌的院内感染预防与控制提供理论依据。方法:收集2022年1~12月临床分离的耐碳青霉烯类肠杆菌目细菌(CRE)。先通过聚合酶链反应(PCR)筛选携带bla_(NDM)基因的CRE菌株,再对菌株携带的其他耐药基因[包括碳青霉烯酶、超广谱β-内酰胺酶(ESBLs)和喹诺酮类耐药相关基因]进行扩增,并测序确认,通过多位点序列分型(MLST)的方法分析相同种属菌株间的亲缘关系。结果:收集的CRE中有2株检测到携带bla_(NDM)基因,其中1株为携带bla_(NDM)-1的弗氏柠檬酸杆菌,另1株为携带bla_(NDM)-5的大肠埃希菌。这两株菌同时携带多个耐药基因,表现为多重耐药。MLST结果显示,产NDM-1型金属酶的弗氏柠檬酸杆菌为ST85型,产NDM-5型金属酶的大肠埃希菌为ST736型,均不是常见流行克隆类型。采用bla_(NDM)探针进行Southern杂交的结果显示,bla_(NDM)-1基因定位于一个~54kb的质粒上,bla_(NDM)-5基因定位于一个~104kb的质粒上,两个携带bla_(NDM)基因的质粒均不能发生接合。结论:首次在平顶山地区报道携带bla_(NDM)基因的CRE菌株;两株菌均同时携带多个耐药基因;bla_(NDM)基因均位于质粒且都与插入序列(IS)移动元件相关,建议进一步加强院感监测及防控,防止耐药菌株的传播和流行。

Objective:To understand the molecular epidemiological characteristics of two clinical isolates of bla_(NDM)-positive Enterobacteriaceae in a hospital in Pingdingshan city so as to provide theoretical support for the prevention and control of nosocomial infection caused by this kind of pathogens.Methods:Clinical isolates of carbapenem-resistant Enterobacteriaceae(CRE)from January to December in 2022 were collected.The bla_(NDM)-positive Enterobacteriaceae were screened using polymerase chain reaction(PCR),and other drug resistance genes[including genes resistant to carbapenems,extended-spectrumβ-lactamases(ESBLs)and quinolones]carried by the strains were subsequently amplified and sequenced,followed by multilocus sequence typing(MLST)to analyze phylogenetic relationship among the strains of the same species.Results:Among the collected CRE,2 strains carried bla_(NDM)genes and were identified as Citrobacter freundii with bla_(NDM)-1 and Escherichia coli with bla_(NDM)-5.These two strains both carried multiple drug-resistant genes and were resistant to multiple common clinical medicines.The MLST result was ST85 for NDM-1-producing Citrobacter freundii and ST736 for NDM-5-producing Escherichia coli,and neither wasa common epidemic clonal type.Southern blot analysis with bla_(NDM)probe showed that bla_(NDM)-1 gene was located on a plasmid with size of~54 kb,and bla_(NDM)-5 gene was located on a plasmid with size of~104 kb.These two bla_(NDM)carrying plasmids could not be conjugated.Conclusion:CRE strains carrying bla_(NDM)genes were reported in Pingdingshan city for the first time.The two reported strains both harbored multiple drug-resistant genes.And bla_(NDM)genes were located on plasmids and related to a mobile element of insertion sequence(IS).It is suggested that surveillance,prevention and control of nosocomial infection should be strengthened to prevent the spread and prevalence of drug-resistant strains.