Molecular Epidemiological Characterization of Two Strains of blaNDM-positive Enterobacteriaceae
Objective:To understand the molecular epidemiological characteristics of two clinical isolates of blaNDM-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 blaNDM-positive Enterobacteriaceae were screened using polymerase chain reaction(PCR),and other drug resistance genes[including genes resistant to carbapenems,extended-spectrum β-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 blaNDM genes and were identified as Citrobacter freundii with blaNDM-1 and Escherichia coli with blaNDM-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 blaNDM probe showed that blaNDM-1 gene was located on a plasmid with size of～54 kb,and blaNDM-5 gene was located on a plasmid with size of～104 kb.These two blaNDM-carrying plasmids could not be conjugated.Conclusion:CRE strains carrying blaNDM genes were reported in Pingdingshan city for the first time.The two reported strains both harbored multiple drug-resistant genes.And blaNDM 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.
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