Aeromonas veronii is a pathogenic bacterium that threatens freshwater fish, including koi carp. Antibiotics used to control bacterial infections can disrupt the intestinal microbiota and promote antibiotic resistance. This study aimed to evaluate the in vitro antimicrobial activity of glutathione (GSH) against A. veronii and its impact on the intestinal microbiota of koi carp. To this end, we examined bacterial growth, biofilm...