Hybrid IncFIA/FIB/FIC(FII) plasmid co-carrying blaNDM-5 and fosA3 from an Escherichia coli ST117 strain of retail chicken

Carbapenems and fosfomycin are important antibiotics used to treat Enterobacteriaceae-associated infections. This study aimed to characterize the co-resistance and co-dissemination mechanism of carbapenem and fosfomycin resistance in an Escherichia coli ST117 strain isolated from retail chicken meat. Antimicrobial susceptibility testing showed that an E. coli CS18F strain had a multidrug resistance profile, including carbapenem and fosfomycin resistance. The presence of blaNDM-5 and fosA3 genes was confirmed by PCR and Sanger sequencing. The bla(NDM-5) and fosA3 genes were successfully transferred to the recipient strain E. coli J53 via conjugation, and the transconjugants had elevated minimum inhibitory concentrations (MICs) for meropenem and fosfomycin. Whole genome sequencing (WGS) of E. coli CS18F revealed that bla(NDM-5) and fosA3 were colocalized on an IncFIA/FIB/ FIC(FII) type plasmid of 189,141 bp, which was designated as pCS18F-NDM-Fos. A novel structure with five IS26 sequences flanking the multiple drug resistance region (MDRR) was identified, and three copies of IS26 were found to be flanked bla(NDM-5), fosA3, dfrA12, aadA2, and sul1. Three types of translocation units (TUs) were identified by PCR, containing either the resistance gene bla(NDM-5) and an IS26 sequence, fosA3, and an IS26 sequence, or both, indicating their potential co-transfer via TUs. Thus, this is an unprecedented report of the presence of a plasmid co-carrying bla(NDM-5) and fosA3 and TUs potentially mediating their simultaneous transfer.

Automated summary

This study characterized the co-resistance and co-dissemination mechanism of carbapenem and fosfomycin resistance in an Escherichia coli strain isolated from chicken meat. The presence of the blaNDM-5 and fosA3 genes was confirmed, and their transferability to another strain was demonstrated. Whole genome sequencing revealed a novel plasmid carrying the blaNDM-5 and fosA3 genes, and the potential transfer of these genes was identified through translocation units.