In vitro beneficial effects of Streptococcus dentisani as potential oral probiotic for periodontal diseases

Background Periodontal diseases are of high prevalence globally and are characterized by an exacerbated inflammatory response which leads to oral tissue destruction. The use of probiotics is widely extended in the case of gastrointestinal disorders; however, their use in microbial-origin oral diseases is still preliminary. Methods We used quantitative polymerase chain reaction to determine the levels of the oral bacterium Streptococcus dentisani 7746 in the tongue, saliva, supragingival, and subgingival plaque. We explore the potential benefits of this probiotic by measuring inhibition of the periodontal pathogens Porphyromonas gingivalis and Fusobacterium nucleatum growth and attachment to human gingival fibroblasts. In addition, its anti-inflammatory activity against cytokines secretion induced by these pathogens was determined in an in vitro model by enzyme-linked immunosorbent assay. Results We report that S. dentisani is found at high levels in the gingival crevice. Data show a strong inhibitory action of S. dentisani supernatant against the periodontal pathogens in pure culture. S. dentisani attached to gingival cells in vitro, inhibiting periodontal pathogens by competition, adherence, and displacement mechanisms. Finally, in a simple in vitro model, the oral probiotic strongly increased the secretion of the anti-inflammatory cytokine IL-10 after incubations with P. gingivalis and F. nucleatum, as well as significantly reduced the expression of interferon-gamma induced by F. nucleatum. Conclusion Altogether, these results highlight the potential of S. dentisani as adjuvant therapy in the management of periodontal diseases, whose efficacy will need to be tested in clinical studies.