Whole-genome analysis of a canine-derived tet(X4)-positive E. coli O15:H45 reveals distinct genomic features.

Multidrug-resistant (MDR) Escherichia coli (E. coli) has emerged as one of the most significant threats to global health, affecting both humans and animals. This study aimed to characterize the genomic features of a distinct MDR E. coli isolate recovered from the abdominal wound of a 10-month-old dog that exhibited weakness. Genomic data were analyzed to identify antimicrobial resistance (AMR) determinants, virulence genes, plasmid, serotype, and MLST. Phylogenetic analyses were performed to investigate the genetic relatedness of the isolate to publicly available E. coli genomes. The dog-derived E. coli was classified as an MDR strain because of its resistance to several tested drugs. Genomic analysis confirmed that the E. coli belonged to serogroup O15:H45, belonging to ST2485, carrying the fimH108 allele. The isolate carried multiple acquired AMR genes, including tet(X4), blaTEM-1B, qnrS1, and sul2. Virulence profiling revealed genes involved in adhesion and toxin production. Whole-genome phylogenetic analysis revealed the evolutionary position of MDR E. coli, and cgMLST assigned it a distinct cgST413080 profile. This study provides genomic insights into a distinct tet(X4)-positive E. coli O15:H45 ST2485 isolate. These findings emphasize the importance of continuous surveillance to monitor the emergence of clinically relevant E. coli lineages in human and animal populations.