The Screening Of Mcr-1 In Enterobacteriaceae Bacteria And The Research Of Correlation Between Mcr -1 And Polymycin Resistant Phenotype In SHENYANG

Objective: Enterobacteriaceae is very important pathogenic bacteria.Alone with the detection rate of carbapenem-resistant enterobacteriaceae increasing,the use of colistin is reintroduced as the last line of defense against multidrug-resistant bacterial infections.The new-found mcr-1 gene carriage is directly related to the colistin resistance,and may be the main reason for the continuous increase of the antimicrobial resistance rate of Enterobacteriaceae.However,there are few studies on the mcr-1 gene carriage rate and related studies in China,and the relevant data regarding the Northeast region of China have not been reported.To screen and analyze the mcr-1 gene in Enterobacteriaceae in Shenyang and to identify the rate of mcr-1 carrying Enterobacteriaceae,as well as its prevalence and resistance state to Colistin.Methods: In this study,2680 clinical isolates of Enterobacteriaceae were collected from five top three hospitals in Shenyang.Among them,2210 Enterobacteriaceae isolates clinically isolated from the First Affiliated Hospital of China Medical University,and other 4 hospital received 470 strains.For all 2680 isolates,mcr-1 gene-specific primers were selected for PCR amplification and agarose electrophoresis to screen the mcr-1 gene.The positive samples were validated by Sanger sequencing.The distribution of 2210 isolates from the First Affiliated Hospital of China Medical University and their bacterial origin and specimen types as well as the resistance to carbapenems were analyzed,and then mcr-1 gene positive strains would be performed by pulse field gel electrophoresis to test the homology of these strains.Colistin susceptibility test would be performed for mcr-1 gene-carrying strains and mcr-1 gene negative strains using Broth Microdilution method to identify a clear rate of resistance.Results: 1.A total of 26 strains of enterobacteriaceae carrying mcr-1 gene were isolated clinically in Shenyang.The carrying rate of mcr-1 gene was about 0.97%(26/2680).Escherichia coli(20/26)and Klebsiella pneumoniae(6/26)were found to carry the mcr-1 gene.Among them,the carriage rate of mcr-1 gene in Escherichia coli was 1.4%(20/1421)and the carriage rate of Klebsiella pneumoniae was 0.8%(6/734).Other Enterobacteriaceae bacteria were not detected carrying mcr-1 gene.2.Escherichia coli carrying mcr-1 gene had a resistance rate of 65%(MIC> = 4 ug / ml)against colistin and the insensitivity rate was 95%(MIC> = 2 ug / ml).Klebsiella pneumoniae mcr-1 gene resistant to colistin 83.3%(MIC> =4ug / ml),the insensitivity rate was 100%(MIC> = 2ug / ml).40 strains of Escherichia coli and 12 strains of Klebsiella pneumoniae in the control group were sensitive to colistin(MIC <= 1 ug / ml).3 PFGE showed there was no monoclonal of the 19 mcr-1 positive strains appear.Conclusion: 1.The mcr-1 gene-carrying Escherichia coli and Klebsiella pneumoniae were found in Shenyang,the carrying rate were 1.4% and 0.8% respectively.2.The mcr-1 gene was associated with colistin resistance.3.The results of pulsed-field gel electrophoresis suggested that there was no outbreak of mcr-1 gene-carrying enterobacteriaceae bacteria occurred in Shenyang.