RESUMEN
Non-lactose-fermenting Escherichia coli (NLFEC) has a few descriptive studies restricted to human infections. In the present study, isolates of NLFEC obtained from urine samples of dogs with hyperadrenocorticism were characterized regarding their virulence ability, biofilm formation capacity and antimicrobial susceptibility profile. Escherichia coli lactose-fermenting strains from urinary infection in dogs with the same conditions were analysed to provide comparisons. The non-lactose-fermenting E. coli strains were classified as belonging to clade I E. coli, whereas the lactose-fermenting strains were classified in phylogroup B2. All strains presented virulence markers to adhesion, iron acquisition, toxins, colicin and cytotoxin production, and biofilm regulation. Components of the extracellular matrix in addition to the in vitro biofilm formation ability were observed in the strains. Multidrug resistance (MDR) profiles were observed by in vitro susceptibility tests to all NLFEC strains. In summary, non-lactose-fermenting uropathogenic E. coli from dogs behaves similar to lactose-fermenting E. coli, exhibiting MDR profile, and pathogenic potential of promote animal infections.