Antibiograms generated in the United States support use of potentiated sulfonamides and intravenous amoxicillin-clavulanic acid when antimicrobials are needed in Escherichia coli canine pyometra.

OBJECTIVE: Evaluate antimicrobial susceptibility patterns among bacterial pathogens isolated from canine pyometra cases and generate a cumulative antibiogram to inform evidence-based treatment recommendations. METHODS: This observational retrospective study included canine uterine samples submitted for antimicrobial susceptibility testing to Idexx Laboratories and the Cornell University Animal Health Diagnostic Center between 2007 and 2023 in the US. Susceptibility results were interpreted according to current Clinical and Laboratory Standards Institute criteria. Cumulative antibiograms were generated with an interactive app for analysis of diagnostic antimicrobial susceptibility test data (AMR Visualizer; RShiny). RESULTS: Across the 2 laboratories, 6,462 bacterial isolates were included. Escherichia coli was the predominant pathogen (71.7%). Among E coli isolates, poor susceptibility was observed to penicillins, β-lactam/β-lactamase inhibitor combinations, tetracyclines, and chloramphenicol. Excellent susceptibility was maintained to aminoglycosides, third-generation cephalosporins, potentiated sulfonamides, and imipenem. Most E coli isolates were susceptible-dose-dependent to fluoroquinolones and susceptible with increased exposure to intravenous amoxicillin-clavulanic acid. CONCLUSIONS: Most canine pyometras are caused by E coli. The in vitro antimicrobial susceptibility patterns of these isolates contribute to understanding resistance trends and support antimicrobial stewardship efforts. Susceptibility should be interpreted in the context of regimens used for breakpoint development. CLINICAL RELEVANCE: When perioperative antimicrobial therapy of pyometras is appropriate, veterinarians can use antibiograms to assist in selecting an effective and appropriate antimicrobial before susceptibility test results are available. These antibiograms suggest that folate-pathway inhibitors could be effective empiric choices that align with antimicrobial stewardship principles. High-exposure intravenous amoxicillin-clavulanic acid could be an effective choice in regions where the product is available.