Abstract
BACKGROUND: Oral nitrate-reducing bacteria are associated with good oral health, with inorganic nitrate specifically promoting the growth of these beneficial bacteria. Sugar alcohols affect the composition of oral microbiota, potentially impacting oral health. The present study aimed to investigate the combined effects of nitrate and sugar alcohols on nitrate-reducing bacteria and nitrate metabolism in oral microbiota cultured in vitro. METHODS: Species-level microbial analysis using 16S rRNA gene sequencing of DNA extracted from the supragingival plaque-derived biofilm cultured under micro-aerobic conditions for 48 h with nitrate and/or sugar alcohols was conducted. Nitrate metabolites, lactate, and pH in culture supernatants were also measured. RESULTS: The combined addition of nitrate and erythritol, but not xylitol or sorbitol, significantly increased the relative abundance of Haemophilus parainfluenzae and Neisseria subflava, which are nitrate-reducing bacteria. This shift was accompanied by a corresponding decrease in Streptococcus oralis, which simultaneously induced an increase in the nitrate-reducing capacity and a decrease in lactate production and acidification from sugar metabolism. CONCLUSIONS: The combination of nitrate and erythritol serve as a preventive and therapeutic approach for periodontitis or dental caries by promoting the growth of oral commensal nitrate-reducing bacteria. However, human clinical studies are required to clarify these beneficial effects.