No change in avilamycin (Surmax^® Premix) minimum inhibitory concentration for Clostridium perfringens isolates recovered from poultry up to 7 years post-approval in Canada.

This article focuses on evaluating the susceptibility of *Clostridium perfringens*, the bacterium causing necrotic enteritis (NE) in broiler chickens, to the antibiotic avilamycin before and seven years after its approval in Canada in 2014. The study compared minimum inhibitory concentrations (MICs) of avilamycin in 89 *C. perfringens* isolates collected from Canadian poultry farms between 2003–2013 (pre-approval) and 2014–2021 (post-approval), finding no significant change in susceptibility. Additionally, the mutation prevention concentration (MPC) of avilamycin was determined to be 8 mg/L, which is below the approved dosing levels in feed, suggesting a low risk of resistance development. The findings support the continued use of avilamycin, a non-medically important antibiotic, for controlling NE in broiler chickens without contributing to antimicrobial resistance concerns relevant to human health.