Capability of probiotics to antagonize the effect of pathogens upon the host

Trabajo presentado en el 13th Congress of Nutrition (CONU), celebrado en Belgrado (Serbia) del 26 al 28 de octubre de 2016The safety and beneficial effect of bacteria present naturally in fermented foods has been demonstrated by its long history of continued human consumption. These microorganisms were included in the food processing technology which has led, at the end of the past century, to the emergence of probiotic products. The rapid global success of probiotics, delivered mainly in dairy products, promoted by FAO / WHO the consensus definition "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host". Probiotic products market is in continuous expansion due to the increasing scientific evidence of their beneficial properties. In this regard, several authors pointed that probiotics will be a powerful tool for the prevention and adjuvant treatment of infections associated with intestinal dysbiosis caused by, among others, antibiotic treatment. However, contradictory results are reported in literature regarding the efficacy of probiotics against clinical relevant pathogens such as Clostridium difficile. There are various possible mechanisms by which probiotics could exert their action, such as: i) the formation of a physical barrier that prevents access of pathogens, or their toxins, to the intestinal receptors, ii) the strengthening of the intestinal barrier by inducing mucus secretion and/or by reinforcing the tight junctions between epithelial cells, iii) the induction of the immune response, and iv) the production of antimicrobial substances. In some of these mechanisms there is a direct competition between probiotics and pathogens for colonizing the intestinal mucosa; this is because both bacterial types have surface molecules (MAAPs, microorganisms-associated molecular patterns) sharing great similarities to each other, and then, both competing for their binding to specific eukaryotic receptors (PRPs, pattern recognition receptors). One of these surface molecules involved in protection of bacteria and in colonization of diverse environments, are exopolysaccharides (EPS) for which beneficial effects have been reported as well.Peer reviewe