Characterization Of bla(NDM-5)-Positive Escherichia coli Prevalent In A University Hospital In Eastern China

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 IS3000-ΔISAba125-IS5-bla(NDM-5)-bleMBL-trpF-dsbC-IS26 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).