Mechanism Of Dissemination Of Carbapenem Resistance Gene Bla_NDM-5 In Clinical Enterobacteriacea

objective:To investigate the spread mechanism of carbapenene-resistant gene bla _NDM-5 in clinical enterobacteriaceae bacteria,and to provide a theoretical basis for clinical anti-infection treatment of such bacteria.Methods:A total of 224 strains of carbapenem resistant enterobacteriaceae bacteria were collected from 4 hospitals in zhejiang province.The drug-resistant phenotype of the strain was confirmed by drug susceptibility test,and the related hydrocarbendene-resistant genes were analyzed by PCR and sequencing.The epidemiological links between the above strains were analyzed by polyclonal site sequence analysis and pulsed field gel electrophoresis.Southern blot hybridization was used to determine the location of drug resistance genes,and conjugation experiment was used to evaluate the gene transfer ability,so as to further analyze the clinical prognosis.Results:Eleven strains of bla _NDM-5,including 9 e.coli,1 klebsiella pneumoniae and 1citrobacter frans,were identified by PCR and sequencing from 224 bacterial strains of enterobacteriaceae with positive drug resistance to carbapenems.The results of MLST and PFGE analysis showed that all 9 escherichia coli strains were of different clone types.S1-PFGE and Southern blotting indicated that the bla _NDM-5 gene was located in a 46kb Inc X3 plasmid.The resistant phenotype of carbapenem was successfully transferred to e.coli EC600 by the strain carrying bla _NDM-5 gene（81.8%）.In addition,further analysis of the whole genome sequence showed that the plasmid was highly similar to most of the plasmids carrying bla _NDM-5 gene reported in China.fuethermore,a review of the clinical data showed that these patients with bla _NDM-5 gene strains had the characteristics of long hospital stay and extensive use of broad-spectrum antibiotics,which was different from previous reports that the gene was found in the community.Conclusion:The data in this study showed that the Inc X3 plasmid mediates the bla _NDM-5gene and plays an important role in the spread of enterobacteriaceae bacteria.In addition,we isolated both e.coli and citrobacter fraseri with bla _NDM-5 gene from a patient,which further indicated the possibility of Inc X3 plasmids mediating the spread of bla _NDM-5 gene between different species.It is urgent to closely monitor the further spread of the bla _NDM-5 gene carrying strain,which should be paid more attention to in clinic.