Promising immunomodulatory effects of selected strains of dairy propionibacteria as evidenced[i] in vitro[/i] and[i] in vivo.[/i]

Selected immunomodulatory probiotic bacteria can counteract inflammation of the intestine through multiple regulatory activities and may be either complementary or an alternative to conventional treatments toward inflammatory bowel disease (IBD), a growing health concern in developed countries. Probiotic strains such as lactobacilli and bifidobacteria are able to induce anti-inflammatory cytokines in human peripheral blood mononuclear cells (PBMCs) in vitro and were shown to exert efficient anti-inflammatory effects on colitis in vivo (9, 26). However, little is known about the immunomodulatory potential of highly consumed starter bacteria such as dairy propionibacteria. Consumption of fermented products has an impact on immune system function (25), and the bacterial content of these products is responsible for immunomodulation (6, 10). Dairy propionibacteria display various probiotic properties either similar to or distinct from those reported for probiotic bifidobacteria and lactic acid bacteria (3). Although an anti-inflammatory potential of a few dairy propionibacterium strains was occasionally suggested in vitro (15) or in animals (22, 24, 31), no reliable observation was established in terms of strain variability and of specific mechanisms involved. In addition, supplementation with dairy propionibacteria in human randomized, placebo-controlled, double-blind trials has mainly concerned mixtures comprising probiotic bacteria assigned to genera other than Propionibacterium but rarely with propionibacteria alone (16). Thus, because of synergistic effects, it is not possible to attribute observed health benefits to a specific bacterium per se within the mixtures.