ABSTRACT
Aims: Five Lactobacillus rhamnosus strains (UBU03, UBU06, UBU09, UBU34 and UBU37) with good in vitro probiotic properties, isolated from breast-fed infants, were evaluated for in vitro adhesion, competitive adhesion and immunomodulatory properties. Knowledge of such properties is important when considering specific circumstances when these strains might be used clinically. Methodology and results: The Caco-2 cell line was used for adhesion assays and for competitive adhesion assays against Escherichia coli O157:H7. Lactobacillus rhamnosus GG was used as the reference strain for adhesion assays. The immunomodulatory activities of the five strains were evaluated by determining the levels of the inflammatory cytokines IL-6, IL-12 and TNF-α, and of the immunoregulatory cytokine IL-10, produced by bacterial-activated THP-1 cells after 6, 12 and 24 h of stimulation. In the cell-adhesion assays, all five strains showed high adhesion properties. For UBU09, UBU34 and UBU37, adhesive capacity was higher than that of the reference strain. All strains except UBU03 showed the ability to inhibit adhesion of E. coli O157:H7 to Caco-2 cells. All strains induced IL-6 production but not IL-12 production. UBU03 and UBU09 could induce only one cytokine IL-6. UBU06 and UBU34 could each induce two (IL-6/IL-10 and IL-6/TNF-α, respectively). UBU37 could induce three cytokines (IL-6/TNF-α /IL-10). Conclusion, significance and impact of study: These five probiotic L. rhamnosus strains with high adhesion properties and with different in vitro cytokine induction profiles should be investigated further in different immunological conditions to identify appropriate circumstances for their clinical use.