Bovine milk fermented with Lactobacillus rhamnosus L8020 decreases the oral carriage of mutans streptococci and the burden of periodontal pathogens

Abstract Aim: The aim of this study was to find the oral isolate of lactobacilli, which has the potential to inhibit either periodontal, cariogenic, or fungal pathogens in vitro, and to examine the effects of bovine milk fermented with the isolate on the oral carriage of cariogenic and periodontal pathogens. Methods: The inhibitory effects of the supernatant of Man–Rogosa–Sharpe broth, in which each of 42 oral isolates of lactobacilli grown, was examined. One isolate, Lactobacillus rhamnosus L8020, that showed the potential to inhibit either periodontal, cariogenic, or fungal pathogens in vitro, was used to examine the effects of fermented milk on the oral carriage of cariogenic and periodontal pathogens, which was examined by a placebo‐controlled and cohort trial using 50 participants. Results: Edible yogurt containing Lactobacillus rhamnosus L8020 significantly reduced the oral carriage of mutans streptococci (P < 0.01) and four periodontal pathogens examined: Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Fusobacterium spp. (P < 0.01), but the phenomenon were not observed with the placebo yogurt (P > 0.05). Conclusion: These results suggest that yogurt with Lactobacillus rhamnosus L8020 could reduce the risk of dental caries and periodontal disease.