ROUNDS

In the spring of 2023, a three-veterinarian mixed practice in suburban Columbus began noticing something troubling in their culture-and-sensitivity results. Escherichia coli isolates from routine urinary tract infections — the bread-and-butter of any small-animal caseload — were returning resistant to enrofloxacin at rates their attending internist had never seen in twelve years of practice. By the time they contacted the Ohio State diagnostic laboratory for a retrospective analysis, the pattern was unmistakable: their fluoroquinolone resistance rate had climbed from 24% to 47% in eighteen months.

They were not an outlier. Data from the National Antimicrobial Resistance Monitoring System's companion animal surveillance arm, compiled across 8,412 isolates submitted from 22 states between 2020 and 2024, reveals a consistent and accelerating upward trend. The figure below illustrates resistance trajectories for the three most commonly isolated gram-negative and gram-positive organisms in companion animal practice.

"The resistance rate is not the crisis. The crisis is that the average practice has no denominator — no idea what their baseline looks like. You cannot steward what you cannot measure."

What makes this data particularly actionable for mixed-practice clinicians is the granularity now available at the regional level. Unlike the broad national averages that shaped the 2023 AVMA antimicrobial stewardship guidelines, the NARMS 2024 companion animal supplement allows practices to benchmark against their specific USDA agricultural district — a meaningful distinction given that fluoroquinolone use patterns in livestock operations within a region demonstrably influence companion animal isolate profiles within a 50-mile radius.