Antimicrobial potential of known and novel probiotics on in vitro periodontitis biofilms

Abstract Several oral diseases are characterized by a shift within the oral microbiome towards a pathogenic, dysbiotic composition. Broad spectrum antimicrobials are often part of their treatment. However, with the rising antibiotic resistance, alternatives are increasingly desirable. Alternatively, supplying beneficial species through probiotics is increasingly showing beneficial results, however, these probiotics are rarely evaluated comparatively. In this study, the in vitro effects of three known- and three novel lactobacillus strains, together with four novel Streptococcus salivarius strains were comparatively evaluated for antagonistic effects on proximal agar growth, antimicrobial properties of probiotic supernatant and the probiotic's effects on in vitro periodontal biofilms. Strain specific effects were observed as differences between genera and differences in efficacy within genera. While some of the lactobacillus candidates were able to reduce the periodontal pathobiont A. actinomycetemcomitans, the S. salivarius strains were not. However, the S. salivarius strains were more effective against P. intermedia, P. gingivalis and F. nucleatum. Most of the lactobacillus strains also negatively affected the prevalence commensal species within the biofilms, while this was lower for S. salivarius strains. Both within lactobacilli and streptococci some strains showed significantly more inhibition of the pathobionts, indicating the importance of proper strain selection. Additionally, some species showed reductions in non-target species, which can result in unexpected and unexplored effects on the whole microbiome.