Open, appendicular fractures are often colonized with pathogenic bacteria at the time of definitive surgical debridement in dogs and cats

Objective: To report the proportion, pathogenic bacterial isolates (PBIs), and colonization rate of open, appendicular fractures in dogs and cats. To evaluate whether the time to antibiotic administration and to definitive surgical debridement was associated with colonization rate, number of PBIs, complication rate, or complication severity. Methods: The electronic medical records of patients transferred to a veterinary referral center's surgery department between September 2019 and August 2024 were reviewed. Data were collected for all dogs and cats transferred with fractures. All cases with open fractures were included for bacterial isolate and antibiotic susceptibility reporting and statistical analysis. Results: 466 dogs and cats were transferred for fracture management. Open fractures occurred in 44 of 357 dogs (12%) and 11 of 70 cats (16%) with appendicular fractures. Thirty-two dogs and 6 cats were included for statistical analysis and had culture results reported. Twenty-one fractures grew 42 PBIs from 15 genera. The most frequently cultured isolates included 22 Enterobacterales and 9 Enterococcus sp. There was an increased frequency of gram-negative aerobes compared to human medicine. There was a 47% complication rate including 3 minor, 13 major, and 1 catastrophic complication. Conclusions: Open fractures in dogs and cats appeared to be colonized with a higher proportion of gram-negative aerobes than human patients. Clinical Relevance: Empiric antibiotic therapy for open fractures in dogs and cats should cover gram-positive and gram-negative aerobes. Monotherapy with penicillins or cephalosporins may not provide sufficient antibiotic coverage due to frequent resistance.