The role of microbiota-derived postbiotic mediators on biofilm formation and quorum sensing-mediated virulence of Streptococcus mutans: A perspective on preventing dental caries

Dental caries is not only one of the most prevalent diseases worldwide, but also a public health problem, undoubtedly. Among the various species of cariogenic bacteria, Streptococcus mutans is considered to be the major etiological pathogen of dental caries. The present study aimed to assess the influence of microbiota-derived postbiotic mediators (PMs) on the pathogenesis of dental caries. Within this aim, the antibacterial (agar diffusion method) and antibiofilm (crystal violet assay) characteristics of PMs derived from Lactiplantibacillus plantarum EIR/IF-1, Lactiplantibacillus curvatus EIR/DG-1, and Lactiplantibacillus curvatus EIR/BG-2 were analyzed against S. mutans (ATCC 25175). According to the results, PMs of the strain EIR/IF-1, isolated from infant feces showed the highest inhibitory effect (pH-dependent). Besides, sub-MIC doses of all PMs eliminated the biofilm formation following the co-treatment and pre-treatment assays. The reduction of cell viability and notable changes in biofilm formation were also confirmed both on glass coverslips and ex vivo human tooth surfaces by confocal laser scanning microscopy and scanning electron microscopy. Moreover, sub-MIC values of PMs down regulated the expression of gtfC, comA, and comX, without any significant growth inhibition. Organic acids, fatty acids, and vitamins in PMs were also reported. Overall, these findings indicated the possible preventive role of microbiota-derived PMs in the pathogenesis of dental caries.