Plasmid-mediated blaNDM-1 gene resistance and transmission of Escherichia coli

Abstract:

Objective To investigate the epidemic status and transmission mechanism of bla_NDM-1 gene-carrying Escherichia coli(E. coli) in a hospital. Methods 92 strains of carbapenem-non-susceptible E. coli were collected from a hospital affiliated to Nanchang University between January and December 2016, bla_NDM-1 gene was screened and other common carbapenemase genes in bla_NDM-1 positive E. coli were also detected. bla_NDM-1 positive E. coli (donor) and E. coli J53 (receptor) was performed conjugation testing, phenotyping of conjugants was validated by antimicrobial susceptibility testing and modified carbapenem inactivation method(mCIM), plasmids of donor strain and conjugator were extracted, bla_NDM-1 gene was located by Southern blot, and horizontally transfer ability of bla_NDM-1 gene was validated. Results Among 92 strains of carbapenem-non-susceptible E. coli, 2 strains were found to carry bla_NDM-1 gene, carrying rate was 2.2%. Other common carbapenemase genes were also found in these two strains of E. coli. Conjugation testing and Southern blot found that bla_NDM-1 gene of these two E. coli strains was located on the plasmid of E. coli strain, and bla_NDM-1 gene of one E. coli strain could be transferred to E. coli J53 through plasmid. Antimicrobial susceptibility testing showed that these two E. coli strains were both resistant to multiple clinically used antimicrobial agents, conjugants obtained similar susceptibility results to the donor bacteria. mCIM showed that these two E. coli strains and their conjugants all produced NDM-1 carbapenemase. Conclusion E. coli carrying bla_NDM-1 gene and producing NDM-1 carbapenemase is found in this hospital, E. coli carrying bla_NDM-1 gene is resistant to most clinically used antimicrobial agents, plasmids can mediate the horizontal transfer of bla_NDM-1 gene.