Clinical audit on antimicrobial stewardship effectiveness in reducing antimicrobial‐resistant bacterial colonisation in hospitalised horses

BACKGROUND: International guidelines support the One Health approach and recommend antimicrobial stewardship programmes (ASPs) in veterinary medicine. National data on antimicrobial-resistant bacterial colonisation rates (AMRb CR) in horses remain limited. OBJECTIVES: To evaluate the effectiveness of an ASP in reducing AMRb CR in a Veterinary Teaching Hospital using a clinical audit. STUDY DESIGN: Clinical audit. METHODS: In Autumn 2021 active AMR surveillance in Perinatology/Reproduction and Internal Medicine Units planned; January-July 2022-first audit cycle (A1); Autumn 2022-review and implementation of antimicrobial use and biosecurity policies; January-July 2023-re-audit (A2) after ASP application. In total, 328 hospitalised horses (foals and adults) were included. Nasal and rectal swabs collected at admission/birth and discharge/euthanasia/death were tested for methicillin-resistant Staphylococci (MRS), third-generation cephalosporins-resistant Gram-negative bacteria (3GCR-GNB) and carbapenem-resistant Gram-negative bacteria (CR-GNB). Fisher's exact test and Mann-Whitney U test evaluated differences in AMRb CR, antimicrobial use, and hospitalisation length between A1 and A2. RESULTS: In A2, there was a significant reduction in overall AMRb CR (foals: OR = 0.27, 95% CI 0-0.87, p = 0.03; adults: OR = 0.39, 95% CI 0-0.77, p = 0.01), in MRS CR (foals: OR = 0.30, 95% CI 0-0.57, p < 0.001; adults OR = 0.42, 95% CI 0-0.83, p = 0.01), in 3GCR-GNB CR (adults: OR = 0.47, 95% CI 0-0.89, p = 0.02; total: OR = 0.53, 95% CI 0-0.87, p = 0.01), and in CR-GNB CR (foals: OR = 0.26, 95% CI 0-0.90, p = 0.03; total: OR = 0.24, 95% CI 0-0.78, p = 0.02). Highest priority critically important antimicrobials use decreased (foals: OR = 0.17, 95% CI 0-0.41, p < 0.001; total: OR = 0.20, 95% CI 0-0.43, p < 0.001), as did antibiotic treatment duration (foals: A1 7.75 ± 11.5, A2 3.70 ± 4.63 days, p < 0.001; adults:A1 3.70 ± 4.63, A2 0.74 ± 2.27 days, p = 0.04), and hospitalisation length (foals ≤30 days old: A1 18.1 ± 18.9, A2 9.77 ± 7.01 days, p = 0.05; total: A1 16.0 ± 15.1, A2 12.6 ± 11.4 days, p = 0.03). MAIN LIMITATIONS: Lack of genotypic analysis and exclusion of the surgery unit. CONCLUSION: This clinical audit confirms the effectiveness of the implemented ASP and supports its adoption in comparable veterinary settings.