Characterization of pHeBE7, an IncFII-type virulence-resistance plasmid carrying blaCTX-m-98b, blaTEM-1, and rmtB genes, detected in Escherichia coli from a chicken isolate in China

Recently, a novel variant of the CTX-M enzyme, CTX-M-98, was detected in Escherichia coil isolates from food animals. However, few plasmids carrying bla(CTX-M-98) have been fully characterized. In this study, we sequenced the complete pHeBE7 plasmid, an 86,015-bp plasmid that contains the bla(CTX-M-98b), bal(TEM-1), rmtB, and traT genes, using whole-genome sequencing. The backbone of pHeBE7 shows a high similarity ( > 99%) to pMC-NDM, which carries the bla(NDM-1) gene, however its mosaic regions remain relatively unique among sequenced plasmids. We discovered that a typical ISEcp1-bla(CTX-M)-IS903 element in the mosaic region harbors the bla(CTX-M-98b), gene. Conjugation and growth competition assays indicate that pHeBE7 can be easily transmitted and that it confers a limited fitness cost to the recipient cell. The genetic characterization of pHeBE7 may improve our knowledge of how antibiotic resistance disseminates in enterobacteria.