Amoxicillin and amoxicillin-clavulanate resistance in urinary Escherichia coli antibiograms of cats and dogs from the Midwestern United States.

BACKGROUND

Antibiograms are stewardship tools that provide antimicrobial resistance data for regional bacterial isolates to guide treatment of infections.

OBJECTIVES

To develop regional antibiograms of urinary Escherichia coli isolates from cats and dogs.

ANIMALS

Escherichia coli isolates cultured from feline (N = 143) and canine (640) urine from 2013 to 2017, from Kansas State University (N = 335) and private practice (N = 448) patients in the Midwestern United States.

METHODS

Retrospective review of urine culture and susceptibility results. Antibiograms were created for 10 commonly used antimicrobial agents using Clinical and Laboratory Standards Institutes guidelines.

RESULTS

No isolates from cats were susceptible to amoxicillin-clavulanate (susceptibility [S] ≤ 0.25/0.12) or amoxicillin (S ≤ 0.25); isolates from dogs had low susceptibility to amoxicillin 53% (S ≤ 8). Conversely, isolates from dogs had high susceptibility to amoxicillin-clavulanate 92% (S ≤ 8/4), despite equal 90th percentile minimum inhibitory concentrations (8 μg/mL) for feline and canine populations. Resistance to other antimicrobials was uncommon (≤7% for isolates from cats, ≤14% for isolates from dogs).

CONCLUSIONS AND CLINICAL IMPORTANCE

The disparity in susceptibility for amoxicillin and amoxicillin-clavulanate between isolates from cats and dogs likely reflects higher breakpoints for urinary tract infections (UTIs) in dogs. Urine concentration data for these antimicrobials in cats might support a UTI-specific breakpoint for cats and increase potential therapeutic options for managing UTIs in cats with first-line antimicrobials. Decreased susceptibility among isolates from dogs to amoxicillin (53%) compared to amoxicillin-clavulanate (92%) might support amoxicillin-clavulanate as a better empirical choice for UTIs in dogs in this geographical region.