Multidrug-resistant Escherichia coli in livestock is an increasing threat to animals and public health. This study aimed to investigate the genomic characteristics and antimicrobial resistance mechanisms of animal-derived multidrug-resistant Escherichia coli.  A clinical strain, B19, was isolated from diarrheic fecal samples collected from sheep in Ningxia, China. The strain was subjected to hybrid second- and third-generation whole-genome sequencing followed by comprehensive annotation. The complete genome (total size 4,901,302 bp; 50.65% GC) exhibited high genomic integrity and plasticity. In silico typing revealed that strain B19 belongs to phylogroup B1, sequence type ST101, and serotype Ont:H38.  Functional analyses revealed enrichment of genes associated with carbohydrate metabolism and cellular processes, indicating strong metabolic adaptability. Secondary metabolite gene clusters, including NRPS-Metallophore and Terpene pathways, suggested potential ecological roles in iron acquisition and stress defense. CARD analysis identified multiple antimicrobial resistance determinants, predominantly against fluoroquinolones, aminoglycosides, and macrolides, along with efflux pump systems (MdtABC, AcrD). Virulence profiling using VFDB revealed abundant adhesion and iron-transport-related genes, supporting a high colonization and survival potential. Overall, strain B19 carries extensive resistance and virulence determinants, highlighting its adaptive genomic strategies and providing valuable insights into the evolution and dissemination of multidrug-resistant E. coli in livestock.

To Cite This Article: Zhu Z, Xu Z, Wu X, Yang L, Liu M, Farooqi S, Li K, 2026. Isolation and whole-genome analysis of multidrug-resistant Escherichia coli from diarrheic fecal samples in a sheep farm in Ningxia, China. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2026.132