The nutritional effect of probiotic Lactobacillus acidophilus on intestinal microbial flora and inhibition of Shiga toxin (Stx۲) gene expression in zebrafish (Danio rerio) exposed to Escherichia coli O۱۵۷:H۷

Nowadays, the use of probiotics is considered an alternative solution instead of using antibiotics. This study aimed to investigate the nutritional effect of probiotic Lactobacillus acidophilus on intestinal microbial flora and inhibition of Shiga toxin (Stx۲) gene expression in zebrafish exposed to Escherichia coli O۱۵۷:H۷. For this purpose, ۶۰۰ zebra fish were divided into four groups with three repetitions including feeding with a commercial diet without probiotics (C and T۳) and feeding with a diet containing probiotics with a concentration of ۱.۵×۱۰۸ cfu ml-۱ (T۱ and T۲). The fish were fed for ۲۴ days. Then T۲ and T۳ groups were exposed to E. coli O۱۵۷: H۷ for ۷۲ hours. Sampling was done on days ۰, ۱۴, ۲۴, and ۲۸. The obtained results showed that feeding with probiotics led to an increase in the growth of lactobacilli in the intestine (p<۰.۰۵). Also, L. acidophilus decreased the expression of the Stx۲ gene in fish exposed to the pathogen (p<۰.۰۵). Therefore, L. acidophilus used in the diet improved intestinal microbial flora and inhibited toxin production in zebrafish exposed to E. coli O۱۵۷: H۷. This pathogen is very important in terms of prevalence, nutritional role, and the effect of intestinal microbial flora in reducing the pathogenicity of E. coli. In addition, zebrafish is an animal model to investigate the pathogenicity of human pathogens. Therefore, the results obtained can be generalized to humans.