Deciphering Streptococcus Mutans From Dental Caries: Integrated Evaluation of Plant-Derived Compounds, Essential Oils and Bismuth Oxide Nanoparticle as Antivirulence Agents

Dental caries is a chronic biofilm-mediated oral disease in which Streptococcus mutans play a major role in disease progression through acid production and biofilm formation. Increasing antimicrobial resistance and the limitations of conventional antimicrobial agents have encouraged the exploration of plant-derived therapeutics and nanotechnology-based alternatives for oral healthcare applications. Methods: Streptococcus mutans was isolated from pediatric dental caries samples and evaluated for biofilm formation, antimicrobial susceptibility, and sensitivity toward selected medicinal plant extracts, essential oils, and phyto-fabricated bismuth oxide nanoparticles using standard microbiological methods, agar well diffusion, and MIC assays. Nanoparticles were characterized using UV–Visible spectroscopy, FTIR, and DLS analysis. Results: Among 60 dental caries samples, 42 (70%) were positive for S. mutans, of which 76.1% were biofilm producers. Antimicrobial susceptibility testing revealed higher resistance to methicillin (47.9%), ciprofloxacin (41.9%), gentamycin (32.6%), and penicillin (32.4%), while clindamycin showed the highest sensitivity (86.86%). Antibacterial activity was evaluated at concentrations of 100–400 µg/µL. Among the plant extracts, Piper betle (24.50 ± 2.64 mm) and Nigella sativa (24.25 ± 1.70 mm) showed the highest inhibition zones. Clove oil demonstrated the highest antibacterial activity among essential oils (25.75 ± 1.50 mm). Among the nanoparticles, aqueous-mediated Piper betle nanoparticles exhibited the highest activity (24.50 ± 1.29 mm). UV–Visible spectroscopy showed absorption peaks at 220–240 nm, while FTIR and DLS confirmed nanoparticle stabilization and nanoscale distribution. Conclusion: Essential oils, medicinal plant extracts, and phyto-mediated bismuth nanoparticles demonstrated significant antibacterial and antibiofilm activity against S. mutans and may serve as promising plant-based nanotherapeutic agents for pediatric dental caries management.