Positive interactions with the microbiota: probiotics.

Rigorous research in the field of probiotics is a fairly new phenomenon although first reports about beneficial effects of specific gut bacteria on human health originated already a century ago. A prerequisite for such a scrutiny has been a definition of criteria for probiotics. Recently, novel molecular technologies have characterized both potential targets of probiotic action, like gut microbiota and established and candidate probiotic strains in more detail. We thus propose here revised criteria for selection ofprobiotics. In addition to several promising clinical studies e.g., in the prevention and treatment of atopic eczema, certain probiotics have been found to maintain intestinal equilibrium by enhancing the gut mucosal barrier via manipulation of expression of several their own and the host's genes. Introduction of genetic engineering has provided advanced tools to amend probiotics' properties in the fight against different inflammatory conditions.