In vitro inhibition of Streptococcus mutans by cardamom essential oil

Dental caries is a biofilm-related disease that disproportionately affects low-income populations due to limited access to expensive treatments. Natural products offer a promising and affordable alternative for preventing cavities. This study investigated the antibacterial and antibiofilm activity of cardamom essential oil (CEO), which contains bioactive compounds such as 1,8-cineole, linalool, and sabinene, against Streptococcus mutans, the primary cariogenic bacterium. Antimicrobial activity was evaluated using agar well diffusion, broth microdilution, biofilm (crystal violet), and cell viability (MTT) assays. The effects of CEO on six virulence-associated genes (gtfB, gtfC, gtfD, ldh, gbpB, and vicR) were analyzed using quantitative PCR. Minimum inhibitory and bactericidal concentrations of CEO were 2.5% and 5.0% (v/v), respectively. At 5.0%, biofilm formation and cell viability decreased by more than 75%, while virulence gene expression was upregulated, indicating a stress response. Among twelve tested essential oils, CEO showed the strongest inhibition of S. mutans growth and biofilm formation. These findings demonstrate the in vitro inhibitory potential of CEO against S. mutans and highlight its promise as a natural, accessible compound for future development of cost-effective oral care formulations. Further validation in polymicrobial and in vivo models will help to confirm and extend these findings toward potential anticariogenic applications.