English: Four different ways in which probiotics defend against pathogens in the intestine. Probiotics compete against pathogens for the same essential nutrients, leaving less available for the pathogen to utilize (A). They bind to adhesion sites, preventing pathogen attachment by reducing the surface area available for pathogen colonization (B). Signaling of immune cells by probiotics results in the secretion of cytokines, targeting the pathogen for destruction (C). Finally, probiotics attack pathogenic organisms by releasing bacteriocins, killing them directly (D). Bermudez-Brito M, Plaza-Díaz J, Muñoz-Quezada S, Gómez-Llorente C, Gil A, Probiotic Mechanisms of Action. Ann Nutr Metab 2012;61:160-174.