Is use of antimicrobial growth promoters linked to antimicrobial resistance in food-producing animals? A systematic review.

Antimicrobial resistance (AMR) poses a global threat to the health of humans, animals and plants, as well as the environment. In recent years, attention has increasingly focused on the role of antimicrobials as growth promoter (AGPs) in livestock. While the mechanism of action of AGPs is still poorly understood, mounting evidence suggests a link between AGP use and AMR. Consequently, several countries and regions have restricted/banned AGP use in livestock. However, such efforts encounter political, financial, social, and cultural challenges. This systematic review aims to investigate the impact of AGP use on AMR in food-producing animals and focused on the emergence of phenotypic resistance in Escherichia coli isolated from livestock exposed to AGPs. Overall, 7000 studies were screened at title, abstract and full text; from these, 10 were deemed eligible for inclusion in this review. Among the 10 selected studies, seven noted significant increase of AMR associated with AGP use. Significantly increased resistance levels to Highest Priority Critically Important Antimicrobials for human health such as ceftiofur, cefotaxime, ciprofloxacin, and nalidixic acid were observed among other antimicrobials. However, the studies revealed high risk of bias underscoring the need for further research. This review provides a deeper understanding of the consequences of AGP use and occurrence of AMR. It highlights the need for implementing efficient surveillance systems and fostering research into suitable alternatives to AGPs. A shift to sustainable husbandry practices including responsible AMU while safeguarding animal health, productivity and farmers' livelihoods are essential for successful policy implementation.