Growth promoting activity, anti-biofilm effect, and down regulation of papC and rcsA genes expression by Medicago sativa (alfalfa) extract

Abstract

Consumption of Medicago sativa (alfalfa) has been linked to infection control in livestock. Therefore, studying the mechanism of this action may lead to the development of enriched food supplements. The purpose of this study was to investigate how M. sativa extract affects the growth of Lacticaseibacillus casei, Lactiplantibacillus plantarum, Staphylococcus aureus, and Escherichia coli. The effects of M. sativa extract on the bacterial cell adherence to Caco-2 cells (Human colon epithelial adenocarcinoma cell lines) and expression of genes involved in the formation of E. coli biofilm were also studied. Generally, in concentrations lower than 100 mg/ml, alfalfa extract had no antimicrobial effect on the probiotic and pathogenic bacteria. However, it not only acted as a growth promoter for two probiotic strains at 2.5% concentration but also increased the antibacterial effect of probiotics supernatants. Furthermore, alfalfa extract reduced the adhesion of pathogenic bacteria to Caco-2 cells. M. sativa extract was identified to inhibit the biofilm formation by E. coli through decreasing the genes expression, papC, and rcsA. As a result, it looks that alfalfa can improve the growth and function of beneficial bacteria, but further studies are needed to elucidate its mechanism of action.