The Cariogenicity Of Streptococcus Mutans Affects Membrane Vesicle Yield

Membrane vesicles (MVs) of Streptococcus mutans (S. mutans) are specialized secretory structures mediating cariogenic functions, yet the relationship between MVs production and cariogenicity remains unclear. Two clinical strains (S. mutans 593 [DMFT ≥ 6] and S. mutans 18 [DMFT = 0]) were compared with reference strain UA159. Adhesion, acid production, and acid tolerance were assessed in vitro. MVs were extracted via differential centrifugation with deuterium oxide (D₂O)-sucrose cushion and characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and bicinchoninic acid (BCA) assay. MVs yield per colony-forming unit (CFUs) was calculated by normalizing protein (BCA) and particle concentrations (NTA) to CFUs. S. mutans 593 showed significantly stronger adhesion, higher acid production, and greater acid tolerance than UA159 and strains 18 (p < 0.05). MVs diameter (144.9 ± 4.3 nm vs. 131.6 ± 6.7 nm and 126.6 ± 2.7 nm), particle concentration (3.77×1011 vs. 2.03×1011 and 1.07×1011 particles/mL), and size distribution increased with cariogenicity (p < 0.05). Normalizing protein (BCA) and particle (NTA) concentrations to CFUs revealed S. mutans 593 produced 2.2-fold and 1.8-fold more MVs than UA159 and strain 18, respectively (p < 0.05). These findings indicate that cariogenicity directly enhances MVs production in S. mutans.