First Report of mcr-10 in a Seafood-Borne ESBL-Producing Enterobacter xiangfangensis Strain.

mcr-10 is among the growing families of newly identified plasmid-mediated mobile colistin-resistance genes. In this study, we identified an mcr-10 gene in a seafood-borne extended-spectrum β-lactamase (ESBL)-producing Enterobacter xiangfangensis. E. xiangfangensis strain, B12-S77, was subjected to whole genome sequencing using Illumina MiSeq and Oxford Nanopore Technologies. Bioinformatic analysis was performed using tools from the Center for Genomic Epidemiology. The minimum inhibitory concentration (MIC) of 19 antibiotics was determined by the broth microdilution method. Transferability of mcr-10-carrying plasmid was investigated by the conjugation experiment. The strain exhibited a multidrug-resistant (MDR) phenotype against more than three classes of antibiotics but remained susceptible to colistin and polymyxin B. mcr-10 was identified on a fused conjugative plasmid of the IncFIB (K):FII (Yp) backbone adjacent to the XerC-type tyrosine recombinase-gene. At least one insertion sequence (IS) was identified in both the downstream and upstream regions of the xerC-mcr-10 conserved region, indicating that this region may contribute to mcr-10 mobilization or integration into the bacterial genome. The strain belonged to sequence type (ST) 143 and carried the nlpI and mrkA virulence genes, which promote fimbrial adhesion or biofilm formation in enteric bacteria. This report provides novel insights into the emergence of mcr-10 in seafood-borne bacteria, and highlights the importance of surveillance in the seafood supply chain.