Identification and genomic characterization of an mcr-10.1-carrying Enterobacter kobei Strain isolated from a kitchen sink

Background The Enterobacter cloacae complex (ECC) is an opportunistic pathogen frequently associated with nosocomial infections. Colistin is considered a last-resort antimicrobial for multidrug-resistant Gram-negative infections; however, the emergence and dissemination of plasmid-mediated colistin resistance genes, particularly mcr variants, have raised significant public health concerns. Among these, mcr-10 has been increasingly detected in ECC isolates from diverse clinical and environmental sources, underscoring the importance of genomic surveillance to elucidate its genetic context and transmission potential. Methods Swab samples were collected from a kitchen sink and cultured for bacterial isolation, followed by species identification using MALDI-TOF MS. Antimicrobial susceptibility was determined by the broth microdilution method, with results interpreted according to EUCAST and CLSI guidelines. Whole-genome sequencing was performed using a hybrid approach combining Illumina short-read and Oxford Nanopore long-read sequencing. Genome annotation and antimicrobial resistance gene detection were conducted using RAST and ResFinder, respectively. Multilocus sequence typing and plasmid replicon typing were performed using the MLST and PlasmidFinder tools. Comparative plasmid analysis was carried out with EasyFig and BLAST Ring Image Generator, while phylogenetic relationships were inferred using a cgMLST-based approach, and the resulting tree was visualized with iTOL. Results The E. kobei isolate (JX24083) exhibited resistance to β-lactams and early-generation cephalosporins but remained susceptible to colistin and polymyxin B. Whole-genome sequencing identified mcr-10.1 on an IncFIB(K)-type plasmid, designated pJX24083-mcr-10.1. Comparative analysis with mcr-10 -positive plasmids from E. kobei or IncFIB-type mcr-10 -positive plasmids from ECC revealed a conserved genetic structure, with xerC upstream and IS 26 downstream of mcr-10 . Phylogenetic analysis of JX24083 together with 48 mcr-10 -carrying ECC isolates showed that several dominant sequence types, including ST681, ST142, and ST1, were distributed across different hosts and countries, indicating the potential for international dissemination. Conclusion The identification of an environmental E. kobei isolate harboring a conserved xerC–mcr-10 plasmid backbone, yet exhibiting phenotypic susceptibility to colistin, highlights the silent dissemination potential of mcr-10 within the ECC and underscores the necessity for sustained One Health–oriented surveillance of environmental reservoirs.