Lactobacillus reuteri AN417 is a newly characterized probiotic strain. The activity of AN417 against oral pathogenic bacteria is unknown. We investigated the antibacterial activity of cell-free L. reuteri AN417 culture supernatant (LRS) against three oral pathogens: Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus mutans. P. gingivalis and F. nucleatum have been implicated in periodontal disease, whereas S. mutans causes dental caries. Exposing these oral pathogenic bacteria to LRS significantly reduced their growth rates, intracellular ATP levels, cell viability, and time-to-kill. The minimal inhibitory volume of LRS was 10% (v/v) against P. gingivalis, 20% (v/v) for F. nucleatum, and 30% (v/v) for S. mutans. LRS significantly reduced the integrity of biofilms and significantly suppressed the expression of various genes involved in P. gingivalis biofilm formation. The L. reuteri AN417 genome lacked genes encoding reuterin, reuteran, and reutericyclin, which are major antibacterial compounds produced in L. reuteri strains. LRS treated with lipase and α-amylase displayed decreased antibacterial activity against oral pathogens. These data suggest that the antibacterial substances in LRS are carbohydrates and/or fatty acid metabolites. Our results demonstrate that LRS has antimicrobial activity against dental pathogenic bacteria, highlighting its potential utility for the prevention and treatment of P. gingivalis periodontal disease.

Dysregulation of infection-derived inflammatory responses has been one of the crucial pathological causes of oral diseases. Even though the organic extracts of Astilbe chinensis have been frequently reported to have anti-inflammatory activity, the study on the extract of A. chinensis inflorescence has yet to be reported. Here, we evaluated the anti-inflammatory efficacy of A. chinensis collected from a variety of regions and seasons and successfully demonstrated that GA-13-6, an ethanol extract of A. chinensis inflorescence collected in a flowering season, inhibited the production of inflammatory mediators and proinflammatory cytokines, such as nitric oxide (NO), tumor necrosis factor (TNF), and interleukin-6 (IL-6) and suppressed the expression of cyclooxygenase-2 (COX2) and inducible nitric oxide synthase (iNOS) both in mRNA and protein levels in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Importantly, we for the first time confirmed that GA-13-6 efficiently inhibited the growth of Porphyromonas gingivalis, Streptococcus sanguinis, and Streptococcus mutans, showing that GA-13-6 possesses antibacterial activity against these pivotal oral pathogens. Thus, GA-13-6 is a potential active ingredient not only for the treatment or prevention of periodontal and dental diseases but many other inflammation-related diseases.