Abstract: 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. Objective: To evaluate the effectiveness of an ASP in reducing AMRb CR in a Veterinary Teaching Hospital using a clinical audit. Methods: 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). Conclusions: Lack of genotypic analysis and exclusion of the surgery unit. Conclusions: This clinical audit confirms the effectiveness of the implemented ASP and supports its adoption in comparable veterinary settings. INTRODUÇÃO: Diretrizes internacionais apoiam a abordagem One Health e recomendam a implementação de programas de uso racional de antimicrobianos (ASP, do inglês antimicrobial stewardship programmes) na medicina veterinária. No entanto, os dados nacionais sobre taxas de colonização por bactérias resistentes a antimicrobianos (CBRA) em cavalos permanecem limitados. Objective: Avaliar a efetividade de um ASP na redução das taxas de CBRA em um Hospital Veterinário Universitário por meio de uma auditoria clínica. Unassigned: Outono de 2021—planejamento da vigilância ativa de resistência antimicrobiana nas Unidades de Perinatologia/Reprodução e Clínica Médica. Janeiro–julho de 2022—primeiro ciclo de auditoria (A1). Outono de 2022—revisão e implementação de políticas de uso de antimicrobianos (AMU) e biossegurança. Janeiro–julho de 2023—reauditoria (A2) após a aplicação do ASP. MÉTODOS: Foram incluídos 328 cavalos hospitalizados (potros e adultos). Swabs nasais e retais coletados na admissão/nascimento e na alta/eutanásia/óbito foram testados para estafilococos resistentes à meticilina (ERM), bactérias Gram‐negativas resistentes a cefalosporinas de terceira geração (BGN‐RC3G) e bactérias Gram‐negativas resistentes a carbapenêmicos (BGN‐RCARB). Fisher's exact e de Mann–Whitney U foram utilizados para avaliar diferenças nas taxas de CBRA, no uso de antimicrobianos e no tempo de hospitalização entre A1 e A2. Results: Em A2, foi observada redução significativa na taxa global de CBRA (potros: OR = 0,27, IC95% 0–0,87, p = 0,03; adultos: OR = 0,39, IC95% 0–0,77, p = 0,01), bem como nas taxas de CBRA por ERM (potros: OR = 0,30, IC95% 0–0,57, p < 0,001; adultos: OR = 0,42, IC95% 0–0,83, p = 0,01), BGN‐RC3G (adultos: OR = 0,47, IC95% 0–0,89, p = 0,02; total: OR = 0,53, IC95% 0–0,87, p = 0,01) e BGN‐RCARB (potros: OR = 0,26, IC95% 0–0,90, p = 0,03; total: OR = 0,24, IC95% 0–0,78, p = 0,02). O uso de antimicrobianos criticamente importantes de maior prioridade diminuiu (potros: OR = 0,17, IC95% 0–0,41, p < 0,001; total: OR = 0,20, IC95% 0–0,43, p < 0,001), assim como a duração do tratamento antimicrobiano (potros: A1 7,75 ± 11,5; A2 3,70 ± 4,63 dias, p < 0,001; adultos: A1 3,70 ± 4,63; A2 0,74 ± 2,27 dias, p = 0,04) e o tempo de hospitalização (potros ≤30 dias de idade: A1 18,1 ± 18,9; A2 9,77 ± 7,01 dias, p = 0,05; total: A1 16,0 ± 15,1; A2 12,6 ± 11,4 dias, p = 0,03). PRINCIPAIS LIMITAÇÕES: Ausência de análise genotípica e exclusão da Unidade de Cirurgia. CONCLUSÃO: Esta auditoria clínica confirma a efetividade do ASP implementado e sustenta sua adoção em contextos veterinários comparáveis.
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Overview
This study audited the effectiveness of an antimicrobial stewardship program (ASP) in reducing antimicrobial-resistant bacterial colonisation in hospitalized horses at a Veterinary Teaching Hospital.
By comparing data before and after ASP implementation, the research demonstrated significant reductions in resistance rates, antimicrobial use, treatment duration, and hospital stay length.
Introduction and Background
International guidelines endorse the One Health approach, promoting integrated action on human, animal, and environmental health.
Antimicrobial Stewardship Programs (ASPs) aim to optimize antimicrobial use to combat resistance.
In veterinary medicine, particularly equine care, data on antimicrobial-resistant bacterial colonisation rates (AMRb CR) are scarce at the national level.
The study addressed this gap by evaluating an ASP’s impact within a Veterinary Teaching Hospital.
Study Objective
To evaluate whether implementing an ASP could reduce the colonisation rates of antimicrobial-resistant bacteria in hospitalized foals and adult horses.
Methods
Study Design: Clinical audit involving two audit cycles conducted before and after the implementation of the ASP.
Timeline:
Autumn 2021: Planning active antimicrobial resistance surveillance in Perinatology/Reproduction and Internal Medicine Units.
January to July 2022: First audit cycle (A1), baseline data collection
Autumn 2022: Policy review and implementation of enhanced antimicrobial use and biosecurity protocols.
January to July 2023: Re-audit (A2) following ASP application.
Population: 328 hospitalized horses (both foals and adults).
Sample Collection: Nasal and rectal swabs taken at admission/birth and discharge/euthanasia/death.
Microbiological Testing: Screening for three key resistant bacterial groups:
Data Analysis: Fisher’s exact test and Mann–Whitney U test compared antimicrobial resistance rates, antibiotic use, and length of hospital stay between the two audit cycles.
Key Results
Antimicrobial Resistance Reductions in Audit Cycle 2:
Overall reduction in antimicrobial-resistant bacterial colonisation rates (AMRb CR):
Foals: Odds Ratio (OR) = 0.27, p = 0.03
Adults: OR = 0.39, p = 0.01
Reduction in methicillin-resistant Staphylococci colonisation:
Foals: OR = 0.30, p < 0.001
Adults: OR = 0.42, p = 0.01
Reduction in third-generation cephalosporin-resistant Gram-negative bacteria:
Adults: OR = 0.47, p = 0.02
Total population: OR = 0.53, p = 0.01
Reduction in carbapenem-resistant Gram-negative bacteria:
Foals: OR = 0.26, p = 0.03
Total population: OR = 0.24, p = 0.02
Antimicrobial Use Changes:
Use of highest priority critically important antimicrobials decreased:
Foals: from 7.75 ± 11.5 days (A1) to 3.70 ± 4.63 days (A2), p < 0.001
Adults: from 3.70 ± 4.63 days (A1) to 0.74 ± 2.27 days (A2), p = 0.04
Hospitalization Length:
Foals (≤ 30 days old): reduced from 18.1 ± 18.9 days to 9.77 ± 7.01 days, p = 0.05
Total population: reduced from 16.0 ± 15.1 days to 12.6 ± 11.4 days, p = 0.03
Limitations
The study did not include genotypic analysis of bacteria, limiting understanding of specific resistance mechanisms or strain relatedness.
The Surgery Unit was excluded from the audit, so findings may not fully reflect resistance dynamics or stewardship impact in surgical patients.
Conclusions and Implications
The clinical audit confirmed that implementing an ASP led to meaningful reductions in antimicrobial-resistant bacterial colonisation among hospitalized horses.
There was a corresponding reduction in the use of critical antimicrobials and shorter treatment durations, indicating improved antimicrobial use practices.
Shortened hospital stays suggest potential benefits for animal welfare and resource use.
The findings support adopting similar ASPs in other veterinary hospitals to combat antimicrobial resistance and promote animal and public health under the One Health paradigm.
Cite This Article
APA
Mazzola K, Lanci A, Piva S, Schisa V, Mariella J, Scarpellini R, Freccero F, De Carolis E, Tumietto F, Castagnetti C.
(2026).
Clinical audit on antimicrobial stewardship effectiveness in reducing antimicrobial-resistant bacterial colonisation in hospitalised horses.
Equine Vet J.
https://doi.org/10.1002/evj.70171
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Lanci, Aliai
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Piva, Silvia
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Schisa, Viviana
Department of Statistical Sciences, University of Bologna, Bologna, Italy.
Mariella, Jole
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Scarpellini, Raffaele
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Freccero, Francesca
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
De Carolis, Erica
Department of Statistical Sciences, University of Bologna, Bologna, Italy.
Tumietto, Fabio
Unit of Antimicrobial Stewardship, Local Health Authority of Bologna, Bologna, Italy.
Castagnetti, Carolina
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Health Science and Technologies Interdepartmental Center for Industrial Research (HST-ICIR), University of Bologna, Bologna, Italy.
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