Evaluating a Targeted Antimicrobial Stewardship Program and Its Temporal Association with Resistance Trends in a Veterinary Referral Hospital

Antimicrobial resistance is an increasing concern in companion animal practice; however, effective mitigation strategies in veterinary referral hospitals remain underexplored. This study investigated whether antimicrobial stewardship interventions guided by hospital-specific resistance patterns and prescribing data could improve resistance outcomes in a secondary care veterinary setting. Using data from 2016 to 2018 at the University of Tokyo Veterinary Medical Center, a targeted intervention was developed and implemented in early 2019, and its impact was evaluated until 2024. The intervention included Gram staining-based presumptive pathogen estimation, antibiogram-guided antimicrobial selection, clinician education, and regular feedback on prescribing practices. By 2020, overall antimicrobial use had reduced by over 50%, with marked reductions in the use of carbapenems and fluoroquinolones. By 2022, the prevalence of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella spp. decreased from 53% to 24% and 78% to 7%, respectively. However, methicillin-resistant staphylococci remained prevalent in approximately 50% of cases. These findings suggest that hospital-tailored antimicrobial stewardship programs may be associated with meaningful reductions in resistance among gram-negative pathogens, although causality cannot be confirmed due to the observational study design. Moreover, additional strategies are necessary to address persistent resistance in gram-positive organisms.