The Effect of Limosilactobacillus fermentum MG4717 on Oral Health and Biosafety.

Oral diseases such as periodontitis and dental caries, as well as conditions related to oral health such as halitosis, are closely associated with dysbiosis of the oral microbiota and continue to pose significant public health challenges worldwide. With the increasing resistance to existing antibiotics and side effects of chemical disinfectants, probiotics have emerged as promising alternatives for oral healthcare. This study aimed to evaluate the oral health efficacy and probiotic properties of Limosilactobacillus fermentum (L. fermentum) MG4717 isolated from the human oral cavity. L. fermentum MG4717 showed notable antimicrobial activity against the key oral pathogens Streptococcus mutans (S. mutans), Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), Porphyromonas gingivalis (P. gingivalis), and Fusobacterium nucleatum (F. nucleatum) and effectively inhibited biofilm formation. Additionally, L. fermentum MG4717 significantly downregulated methionine gamma-lyase (mgl) mRNA expression in P. gingivalis, which is implicated in halitosis and pathogenicity. L. fermentum MG4717 strongly adhered to the KB and HT-29 epithelial cells and exhibited good resilience under simulated gastrointestinal conditions. Whole-genome sequencing (WGS) and average nucleotide identity (ANI) analysis confirmed strain identity (98.73% average nucleotide identity with L. fermentum DSM20052) and the absence of transferable antibiotic resistance genes. Safety assessments revealed no cytotoxicity, hemolytic activity, or bile salt hydrolase activity. These findings suggest that L. fermentum MG4717 has the potential to be used as a safe and effective oral probiotic beneficial for oral health.