Understanding veterinarians' antibiotic choices and eliciting acceptable non-inferiority margins for randomized trials: a multi-country study.

Objectives: Unnecessary antibiotic use is a problem in both human and veterinary medicine. A clear understanding of prescribing behaviours and the underlying drivers is required to design studies that can provide the necessary evidence to identify areas or populations where antibiotics can safely be reduced. Methods: We conducted three discrete choice experiments to evaluate prescribing behaviour in different clinical scenarios where antibiotics are frequently part of case management: canine acute diarrhoea (CAD), post-operative prophylaxis (SAP), and urinary tract infection (UTI). We estimated acceptable non-inferiority margins for clinical trials (i.e. the maximum outcome loss clinicians would accept in exchange for reduced antibiotic use) for CAD and UTI. A total of 1219 small animal veterinarians across six global regions were surveyed. Results: Key drivers of prescribing behaviour included severity of clinical signs (CAD), anticipated clinical and microbiological cure rate (UTI), and risk of surgical site infection (SAP). Client pressure also impacted on prescribing decisions in all scenarios. In two of three scenarios, CAD and UTI, potentially acceptable non-inferiority margins were identified: 0-2 days for CAD duration without antibiotics; and 10% for clinical and microbiological cure in UTI cases. We found substantial geographical variation in prescribing habits, with higher rates in Asia and Southern/Eastern Europe. Conclusions: Results highlight problematic areas for targeting reduction measures but should support the development of antimicrobial stewardship guidelines aiming to reduce unnecessary antibiotic use.