Genetic Characterization of a Linezolid- and Penicillin-Resistant Isolate Co-Harboring and .

Linezolid and penicillin are critical for treating multidrug resistant (MDR) Gram-positive infections, but the emergence of resistance to both seriously threatens public health. Here, we first report the cocarrying (oxazolidinone resistance) and (β-lactam resistance) genes by the plasmid in a strain of HDC14-2 derived from porcine. The isolate also exhibits MDR phenotypes to phenicols, oxazolidinones, tetracyclines, β-lactams, aminoglycosides, macrolides, and lincosamides. Whole-genome sequencing (WGS) revealed these resistance genes, along with (), (), , (B), ()-(), , , (E), (B), , and , were clustered in a novel MDR region flanked by IS elements on plasmid pHDC14-2.133K. This IS-bounded MDR region formed translocatable units (TUs), including an IS- TU that was also identified on a secondary plasmid, pHDC14-2.27K. Functional assays demonstrated the excisability and mobility of these TUs, indicating its potential ability integration into other plasmids or chromosomes. Critically, electrotransformation confirmed the transfer of pHDC14-2.27K (-carrying) to JH2-2, with retained TU activity and minimal fitness cost. This study provides the evidence of colocalized and on plasmids in enterococci, highlighting their role in disseminating pan-resistance among bacteria. Although is not an important pathogenic bacterium to humans and animals, but its potential risk to horizontally spread of these resistance genes important in medicine still cannot be ignored.