Characterisation of blaNDM-5-bearing IncHI2 plasmid from Escherichia fergusonii in China

Abstract

Objective

Carbapenems are considered to be the last resort for serious infections caused by multidrug-resistant Gram-negative bacteria, and the emergence of carbapenem-resistant Enterobacteriaceae has posed a serious threat to human health. However, carbapenem resistance is rarely reported in Escherichia fergusonii. In this study, a New Delhi metallo-β-lactamase (NDM)-5-producing E. fergusonii strain, EFSXRJ10, was isolated from a chicken in China.

Methods

Minimal inhibitory concentrations were determined using broth microdilution-based antimicrobial susceptibility testing. The complete genome sequence of the NDM-positive isolate was obtained using the Illumina NovaSeq and Oxford Nanopore GridION sequencing platforms, followed by hybrid assembly with Unicycler. In the plasmid conjugation assay, a sodium azide–resistant Escherichia coli strain, J53, was employed as the recipient.

Results

Strain EFSXRJ10 was resistant to ampicillin, amoxycillin-clavulanic acid, gentamicin, spectinomycin, tetracycline, florfenicol, sulfafurazole, cefotaxime, ceftazidime, apramycin and meropenem. The bla_NDM-5 gene was located on the IncHI2 plasmid, which can be transferred by conjugation at a frequency of (4.78 ± 0.67) × 10^–5. The bla_NDM-5-carrying plasmid, which harbours 14 antibiotic resistance genes belonging to the IncHI2/ST3 type and exhibiting high similarity to other bla_NDM-5-carrying IncHI2 plasmids, was deposited in GenBank. The genetic structure containing bla_NDM-5 was organised as ‘IS3000-ΔISAba125-IS5-ΔISAba125-bla_NDM-5-ble_MBL-trpF-dsbD-IS26-∆umuD-∆ISKox3-∆IS3000’.

Conclusions

This is the first report characterising the bla_NDM-5-bearing IncHI2 plasmid in E. fergusonii. Surveillance and control measures should be implemented to halt transmission of bla_NDM-5 in food animals.