By Rachelshoemaker CC BY-SA 4.0
Four different mechanisms under research by which probiotics may defend against pathogens in the intestine. Probiotics may compete against pathogens for the same essential nutrients, leaving less available for the pathogen to utilize (A). They may bind to adhesion sites, preventing pathogen attachment by reducing the surface area available for pathogen colonization (B). Signaling of immune cells by probiotics may result in the secretion of cytokines, targeting the pathogen for destruction (C). Finally, probiotics may attack pathogenic organisms by releasing bacteriocins, killing them directly.