CONICET | Buscador de Institutos y Recursos Humanos

Aim: To asses whether a comparative in vitro evaluation of the biological properties of different Bifidobacterium longum strains could lead to a better definition of the probiotic concept linked to the in vivo functionality of the so-called probiotic strains. Methods: Eight different B. longum strains including human commensals and reference strains were studied. The ability of these strains to interact with the host was comparatively evaluated by assaying their adhesion to mucin and their immunomodulatory properties. Results: The studied B. longum strains showed significantly different adhesion ability to mucin. The adhesion of these strains ranged from 2 to 11 %. The probiotic strains were not those showing the highest adhesion although this has been considered to be a positive trait of probiotics to ensure their residence and interaction with the human host. The studies of mechanisms of adhesion of these strains pointed for a role of proteins associated to the cell-envelop of bifidobacterias. In addition, the strains showed differences in their ability to stimulate cytokine production by PBMC, leading to differential increases in inflammatory and regulatory cytokines. Summary: Bifidobacterium strains belonging to the same species showed remarkable differences in the biological properties related to their interaction with the host epithelial surface and immune system. The properties of particular probiotic strains were not always those desired according to the criteria generally accepted for their selection (FAO/WHO, 2002) Conclusion: The establishment of links between in vitro and in vivo evaluation tests of probiotic strains as well as the identification of biological markers of their functional traits will be of pivotal importance for a rational definition of what makes a strain be considerer as a probiotic.