Genomic characterization of a multidrug-resistant isolate co-harboring and on distinct plasmids.

BACKGROUND

is an emerging multidrug-resistant (MDR) pathogen within the genus. Although individual occurrences of or have been sporadically reported, the coexistence of both carbapenemase genes in a single strain remains extremely rare.

METHODS

We performed whole-genome sequencing and conjugation assays on a bloodstream isolate of (JH112) obtained from a critically ill patient. Plasmid structure, resistance determinants, and transferability were comprehensively analyzed using assays and bioinformatic pipelines.

RESULTS

JH112 exhibited an extensively drug-resistant phenotype and carried two major carbapenemase genes, and , located on distinct plasmids. The gene resided on an IncFII(Yp)-type plasmid (∼110 kb) with a complete conjugation module and was successfully transferred to a recipient strain. This plasmid also harbored an O-antigen biosynthesis gene cluster, potentially enhancing host adaptation. In contrast, the gene was located on a 340 kb IncHI2/HI2A-type megaplasmid with incomplete conjugation machinery and failed to transfer under standard conditions. Both plasmids showed unique structural arrangements compared to known references. The chromosome also carried and , contributing to broad-spectrum resistance.

CONCLUSION

We report a rare clinical isolate co-harboring two carbapenemase genes on genetically distinct plasmids with divergent mobility. This highlights the species' potential role as a resistance gene reservoir and the need for enhanced molecular surveillance in both clinical and environmental settings.