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

Abstract                                        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                        &lt; 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                        &lt; 0.001; total: OR = 0.20, 95% CI 0–0.43,                       p                        &lt; 0.001), as did antibiotic treatment duration (foals: A1 7.75 ± 11.5, A2 3.70 ± 4.63 days,                       p                        &lt; 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.