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

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 blaNDM-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 blaNDM-5-carrying plasmid, which harbours 14 antibiotic resistance genes belonging to the IncHI2/ST3 type and exhibiting high similarity to other blaNDM-5-carrying IncHI2 plasmids, was deposited in GenBank. The genetic structure containing blaNDM-5 was organised as 'IS3000-ΔISAba125-IS5-ΔISAba125-blaNDM-5-bleMBL-trpF-dsbD-IS26-∆umuD-∆ISKox3-∆IS3000'.

CONCLUSIONS

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