Invited review: Milk kefir microbiota-Direct and indirect antimicrobial effects

Kefir is a fermented dairy product with well recognized probiotic properties. Recently, consumer interest in fermented products with probiotic microorganisms has increased due to the accumulating evidence of the effects of kefir microorganisms on the modulation of gut microbiota and their antimicrobial activity. Although the health properties of kefir have been reviewed in other works, the present review addresses the antimicrobial effects of kefir microbiota and associated compounds. The antimicrobial activity of kefir microorganisms could derive from different mechanisms. The microorganisms' capacity to adhere to the intestinal epithelium, preventing the adhesion of pathogens, and their immunomodulation properties are among the mechanisms suggested. Bacteria and yeast isolated from kefir have been shown to have in vivo and in vitro antimicrobial activity against enteropathogenic bacteria and spoilage fungi. However, most reports have focused their approach on single-strain antimicrobial properties; evaluation of antimicrobial activity of cocultures of kefir microbiota and their potential mechanisms of action has been neglected. Kefir microbiota and associated compounds have shown promising antimicrobial effects; however, more research needs to be done to discern the mechanisms of action.