Antimicrobial Resistance of Escherichia Coli Strains Isolated from Urine of Women with Cystitis or Pyelonephritis and Feces of Dogs and Healthy Humans

Objective: To assess the prevalence and patterns of antimicrobial resistance among Escherichia coli strains isolated from the urine of women with cystitis or pyelonephritis and from fecal samples from dogs and healthy humans.

Design: Cross-sectional survey.

Sample Population: Escherichia coli isolates from 82 women with cystitis, 170 women with pyelonephritis, 45 dogs, and 76 healthy human volunteers.

Procedure: Susceptibility to 12 antimicrobial agents was determined by means of disk diffusion testing as specified by the NCCLS.

Results: Overall, the 4 most common antimicrobial resistance patterns were resistance to ampicillin, sulfisoxazole, trimethoprim, and trimethoprim-sulfamethoxazole (n = 45 [12% of all isolates]); ampicillin alone (33 [9%]); ampicillin and sulfisoxazole (29 [8%]); and sulfisoxazole alone (14 [4%]). None of the isolates were resistant to ceftazidime, ciprofloxacin, nitrofurantoin, or piperacillin-tazobactam. Resistance was significantly more common and extensive among isolates from women with cystitis or pyelonephritis than among isolates from healthy humans or dogs. Resistance was least common among isolates from dogs. The only resistance phenotype that was more common among canine isolates than human isolates was resistance to sulfisoxazole alone.

Conclusions And Clinical Relevance: Results suggest that dogs are unlikely to be an important external reservoir of antimicrobial-resistant E. coli strains causing infections in humans. On the contrary the data suggest that dogs conceivably could acquire resistant E. coli strains from humans.