The emergence and dissemination of plasmid-mediated resistance to tigecycline, colistin, and carbapenems in Escherichia coli pose a serious public health threat. This study intended to reveal the genomic characteristics of E. coli isolates resistant to these last-resort antibiotics recovered from minks. A total of 100 samples were collected from 25 farmed minks obtained post-slaughter from a single commercial fur farm, with four tissue types sampled per animal including liver, lungs, spleen, and intestine. Following phenotypical characterization all resistant isolates were characterized by Illumina short-read whole-genome sequencing and six representative isolates were further subjected to CycloneSEQ long-read sequencing to reveal complete genomic profile. Conjugation and fitness cost assays were employed to evaluate the transfer rate and biological burden of resistance genes. Collectively, 25 E. coli isolates were recovered that harbor one or more plasmid-mediated antimicrobial resistance genes mcr-1, tet(X4), or bla_NDM-5, imparting resistance to colistin, tigecycline, and carbapenems, respectively. Among these, mcr-1-positive isolates accounted for 52% (n=13), while tet(X4), and bla_NDM-5 were each detected in 24% (n=6) isolates. The resistant E. coli strains exhibited diverse sequence types, predominantly ST746, ST219, and ST641.The tet(X4) gene was located on ~190kb hybrid IncFIA (HI1)/HI1B(R27)/HI1A plasmid, whereas mcr-1 and bla_NDM-5 were associated with IncI2, IncX4, IncHI2, and IncX3, IncB/O/K/Z plasmid types respectively. Moreover, the virulence profile revealed that all E. coli isolates belong to ExPEC (UPEC) pathotype. At present, this study represents the first identification of tet(X4)-positive E. coli and carbapenem-resistant bla_NDM-5-positive E. coli coexisting with colistin resistant mcr-1 gene from minks in China. This study emphasizes the need of continued surveillance to observe the pervasiveness and dissemination of emerging ARGs in minks.

To Cite This Article: Munir A, Shoaib M, Lv Y, Song R, Feil EJ, Wang Z and Li R, 2026. Genomic characterization of plasmid-mediated tet(x4), mcr-1, and bla_ndm-5 genes in Escherichia coli from farmed minks highlights their role as a one health reservoir. Pak Vet J, 46(6): 1525-1535. http://dx.doi.org/10.29261/pakvetj/2026.144