Comparative inhibition of oral pathogens, biofilm formation, and inflammation-related responses by postbiotics from Lactobacillus kefiranofaciens DD2.

BACKGROUND: Postbiotics derived from lactic acid bacteria are attracting significant interest as safe and stable alternatives to live probiotics for controlling oral biofilms and inflammation. OBJECTIVE: Building on previous research that identified Lactobacillus kefiranofaciens DD2 as a potent anti-cariogenic strain, we compared antimicrobial, anti-biofilm, and anti-inflammatory properties of postbiotics produced by DD2 with those from two newly isolated kefir strains (LKF4 and LK12) and two commercial probiotics, Lactiplantibacillus plantarum ATCC 3105 and Lacticaseibacillus rhamnosus ATCC 7469. MATERIALS AND METHODS: Cell-free postbiotics were evaluated for their antimicrobial and anti-biofilm activities against major oral pathogens, including Streptococcus mutans, Streptococcus sobrinus, Porphyromonas gingivalis, and Porphyromonas gulae. Furthermore, their immunomodulatory effects were investigated in lipopolysaccharide-stimulated RAW 264.7 macrophages through nitric oxide assays and reverse transcription quantitative polymerase chain reaction. RESULTS: All tested postbiotics significantly inhibited planktonic growth and biofilm formation of the pathogens (p < 0.05), and DD2 consistently demonstrated the strongest suppression across all species. In macrophages, DD2-derived postbiotics markedly reduced the expression of pro-inflammatory mediators (Cox2, Nos2, Tnf-α, and Il-1β) to approximately 0.5-fold relative to the control, while inducing the highest levels of the anti-inflammatory cytokine Il-10. DD2 upregulated Tlr4, Nrf2, and Ho-1 mRNA, indicating the preservation of pathogen sensing and the activation of cytoprotective pathways via the Nrf2/Ho-1 signaling axis. Notably, this multi-targeted approach highlighted DD2's superior efficacy compared to other kefir and commercial strains. CONCLUSIONS: These findings support the potential of DD2-derived postbiotics as bioactive alternatives for managing oral pathogens, biofilm formation, and inflammation relevant to oral health. Further studies are needed to identify the active components and to validate these effects in oral in vivo models.