What are best practices for antimicrobial stewardship in equine practice?

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Antimicrobial stewardship (AMS) in equine practice rests on five interconnected pillars: restricting use to confirmed or highly probable bacterial infections, prioritizing first-line narrow-spectrum agents, obtaining culture and susceptibility data before escalating therapy, limiting perioperative prophylaxis to the day of surgery, and implementing formal tiered prescribing frameworks with mandatory justification for higher-tier drugs. The threshold question is whether antimicrobials are indicated at all. Approximately 30% of equine patient visits at a northeastern US veterinary teaching hospital received antimicrobials in 2021, and very few of those cases were given antimicrobials without clinical evidence of infection.1 Avoiding prescriptions in cases with no clinical evidence of infection, and in clean surgeries when appropriate, is the foundational stewardship act.1 Antimicrobials are indicated only when thorough patient evaluation and sound clinical judgment indicate a high likelihood of bacterial infection and that antimicrobials are needed to promote recovery.14 First-line injectable therapy should be procaine penicillin combined with gentamicin sulfate in most infectious scenarios, with trimethoprim-sulfadiazine (TMPS) as the recommended first-line oral agent — and in the UK, TMPS is the only licensed oral choice in horses.7 Potentiated sulfonamides are the most commonly used antimicrobial class in equine practice across Europe and the UK.3 Aminoglycosides and potentiated sulfonamides are the most commonly prescribed classes in equine referral practices in the US.8 Although aminoglycosides are classified as critically important antimicrobials (CIA), their use in equine practice is considered standard of care because no alternative gram-negative spectrum antimicrobial of lower human health importance exists.1 High-priority critically important antimicrobials (HPCIAs) — fluoroquinolones and third- and fourth-generation cephalosporins — must be reserved for cas