Characterization Of blaNDM-5-Positive Escherichia coli Prevalent In A University Hospital In Eastern China

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Purpose: The emergence and spread of carbapenem-resistant Enterobacteriaceae deserves special concern worldwide. Unlike the epidemiological characteristics reported in other studies, we found that the production of New Delhi metallo-β-lactamase 5 was the main mechanism for the resistance of Escherichia coli to carbapenems. Methods: All carbapenem-resistant strains were collected from July 2017 to July 2018 of the First Affiliated Hospital of Nanjing Medical University. The presence of carbapenemase-encoding genes was detected using PCR and gene sequencing. Genetic relatedness of the bla NDM-5 -positive E. coli strains was determined with PFGE and MLST. Susceptibility profiles were measured with broth microdilution method and E-test strips. Transferability features of bla NDM-5 gene were assessed by conjugation experiments, S1-PFGE, southern blotting and PCR-based replicon typing methods. The genetic structures surrounding bla NDM-5 were acquired by whole genome sequencing and PCR mapping. Results: Among the 28 carbapenem-resistant E. coli strains, 18 (64%) were verified as NDM-5 producers. The 18 bla NDM-5 -positive E. coli strains showed high resistance to most antibiotics, but 100% were sensitive to colistin and tigecycline. In addition, the 18 bla NDM-5 -positive E. coli strains belonged to eight STs, among which ST167, ST410 and ST101 were found to cause clonal spread in the hospital. Further studies found that the bla NDM-5 gene was located on an IncX3-type plasmid, and all plasmids harbored an IS 3000-Δ IS Aba125 -IS 5-bla NDM-5 - ble MBL- trpF-dsbC -IS 26 structure. Conclusion: The clonal spread of bla NDM-5 -positive E. coli strains and horizontal dissemination via the pNDM-MGR 194-like plasmids should draw more attention. Appropriate infection control operations should be performed to prevent the further spread of bla NDM-5 .