Multidrug resistance in pathogenic Escherichia coli isolates from urinary tract infections in dogs, Spain

This study analyzes antimicrobial resistance and virulence factors in Escherichia coli (E. coli) isolates from dogs with urinary tract infections (UTIs) in Spain. The isolates showed high phenotypic resistance to first- to third-generation cephalosporins, followed by penicillins, fluoroquinolones, and amphenicols. Moreover, 13.46% of the isolates were extended-spectrum beta-lactamase (ESBL) producers, and 71.15% were classified as multidrug-resistant. A strong correlation between resistance genes and phenotypic resistance was observed. Most isolates were identified as extraintestinal pathogenic E. coli, with some harboring virulence factors associated with diarrheagenic pathotypes. Interestingly, isolates with lower antibiotic resistance carried higher levels of virulence factors, although the underlying mechanisms remain unclear. The findings highlight the need for regular antimicrobial resistance monitoring and the revision of therapeutic guidelines for canine UTI to address emerging resistance patterns.