Role of probiotics, prebiotics, synbiotics and postbiotics in inhibition of pathogens

A microbial pathogen is a potentially armed opportunist entity to colonize intestinal mucosa. They have phenomenal ability to evolve and adapt accordingly which further seizes signalling molecules and pathways of host to become pathogenic. In order to colonize mucosal layer, they need to cross the physicochemical barrier formed by intestinal epithelium. This gastrointestinal (GI) epithelium with inhabitant microbiota acts as synergistic partners in system of defense that protect the host from intrusion into GI tract. Resident microbiota ferment carbohydrates to lower the luminal pH by production of organic acids to attenuate gene expression of toxin genes in pathogens, they down regulates proinflammatory cytokine production induced by pathogens, displays competitive exclusion with pathogenic bacteria for attachment sites and nutrition and enhance the barrier integrity. Among them, Lactobacillus and Bifidobacterium species (members of Lactic acid bacteria) are found to be the most active inhabitant that provides better therapeutic benefits. Consumption of these live health beneficial microorganisms in adequate amounts constitutes probiotics. Colonial microbiota can be modified by some potential non digestible oligosaccharides known as prebiotics. These sugars transforms gut microflora towards healthier composition. They are not only found to enhance anti-pathogenic ability and survival of probiotic microorganisms as synbiotic synergy but a few of them have an immense capability to mimic adhesion sites of pathogens thereby providing cytoprotection to intestine. Recent studies also demonstrate anti-pathogenic action of postbiotic metabolites obtained from these lactic acid bacteria. Antimicrobial potency can be further enhanced by creation of recombinant designer probiotics expressing oligosaccharide receptors for adhesins and toxins of pathogens on surface. This chapter illustrates anti-pathogenic mechanisms and actions of probiotic microorganisms alone as live or dead cells or in combination with prebiotics achieved through interaction with pathogenic bacteria.