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Dental Polymethyl Methacrylate Microplastics Induce Biofilm Formation In Streptococcus Mutans
Summary
Researchers found that microplastics shed from plastic dentures (made of PMMA, a common dental material) significantly increased the growth, biofilm formation, and antibiotic resistance of Streptococcus mutans — the main bacterium responsible for tooth decay — in both lab cultures and in mice. The findings suggest that plastic dental devices are an overlooked source of oral microplastic exposure that could worsen dental disease and antibiotic resistance.
This study investigates the in vitro and in vivo effects of polymethyl methacrylate (PMMA)-derived micro/nano-plastics (MNPs)—generated through denture abrasion—on Streptococcus mutans (S. mutans) growth and biofilm formation, given their emerging role as pollutants capable of altering oral microbiota and posing health risks. The 4-week-old male C57BL/6 mice were given oral gavage of 20µm and 80nm PMMA-MNPs for consecutive 4 weeks. We analyzed the abundance dynamics of Streptococcus within the oral microbial community via 16S rRNA sequencing. In vitro experiments, S.mutans was exposed to varying concentrations of 20µm and 80nm PMMA-MNPs, and growth curve was measured. The effects of PMMA-MNPs on S.mutans biofilms were evaluated through crystal violet staining, scanning electron microscopy, and live/dead bacterial staining. Concurrently, changes in extracellular polysaccharides(EPS) and antibiotic resistance of S.mutans were measured. Exposure to PMMA-MNPs resulted in a significant increase in the relative abundance of Streptococcus within the oral microbiota of mice. In vitro co-culture experiments, we demonstrated that PMMA-MNPs markedly enhanced the growth, biofilm formation, and EPS synthesis of S.mutans. Additionally, we also found that exposure to PMMA-MNPs enhanced bacterial antibiotic resistance. Our study demonstrated that PMMA-MNPs promoted the proliferation and biofilm formation of S.mutans, while enhancing bacterial virulence and antibiotic resistance.