Probiotic intervention modulates volatile sulfur compound-associated pathways and oral microbiome balance in ligature-induced periodontitis rats

Background Halitosis is driven by volatile sulfur compounds (VSCs) produced by anaerobic oral bacteria and commonly worsens with periodontitis. We investigated whether the probiotic complex Complex OK suppresses VSC pathways, modulates oral dysbiosis, and reduces inflammation.Materials and methods Complex OK was evaluated in vitro for downregulating the VSC-related mgl gene and antagonism against malodor pathogens using a 1:1 co-culture of Lactobacillus gasseri HHuMIN D and Lacticaseibacillus paracasei OK. In vivo, ligature-induced periodontitis was created in 45 male Sprague-Dawley rats assigned to healthy control, periodontitis control, or low-, medium-, and high-dose groups (0.2, 2, and 20 mg/head/day, corresponding to approximately 10^7, 10^8, and 10^9 CFU/head/day, respectively) treated for 5 weeks. Endpoints included body weight, saliva secretion, tongue coating index (TCI), alveolar bone loss, systemic IL-1β, and oral microbial composition.Results Complex OK reduced mgl expression and inhibited Streptococcus mutans (98.2%), Fusobacterium nucleatum (91.2%), Porphyromonas gingivalis (99.1%), and Prevotella intermedia (96.6%). High-dose supplementation increased body weight (329.02 ± 14.59 g) and saliva secretion (4.03 ± 2.06 mg), lowered TCI (6.40 ± 2.60), decreased Fusobacterium abundance, reduced IL-1β, and showed a non-significant trend toward reduced alveolar bone loss compared with periodontitis controls.Conclusion(s) Complex OK may represent a noninvasive probiotic strategy for modulating halitosis-associated molecular pathways, supporting oral microbiome balance, and reducing periodontal inflammation, with potential as an adjunctive therapy for periodontal care pending further clinical validation.