Virulence genotypes and phylogenetic background of fluoroquinolone-resistant and susceptible Escherichia coli urine isolates from dogs with urinary tract infection

The origins and virulence potential of fluoroquinolone-resistant (FQ-R) Escherichia coli from dogs with urinary tract infection (UTI) are undefined. Therefore, fluoroquinolone-resistant (n = 38) or susceptible (n = 62) E. coli urine isolates from dogs with UTI were characterized for phylogenetic group (A, B1, B2, D) and 61 virulence-associated genes by multiplex PCR, then were compared according to these characteristics. Compared with fluoroquinolone-susceptible (FQ-S) isolates, the fluoroquinolone-resistant isolates exhibited significantly lower prevalences for most virulence genes studied (albeit higher prevalences for several, including iutA: aerobactin receptor), significantly fewer virulence genes per isolate, and shifts away from virulence-associated group B2. Nonetheless, 26% of fluoroquinolone-resistant isolates qualified as extraintestinal pathogenic E. coli (ExPEC), suggesting possible human virulence potential. The findings call into question whether the fluoroquinolone-resistant E. coli encountered in dogs arise through conversion of fluoroquinolone-susceptible canine resident strains to resistance, or instead are imported from an external source. They also identify dogs as a possible reservoir of drug-resistant ExPEC for transmission to other pets and humans.