Antibacterial Effects of Black Cumin Seed Oil on Oral Microcosm Biofilms

Interest in natural extracts for managing oral biofilms is increasing, with black cumin seed oil (BCSO) demonstrating efficacy against Streptococcus mutans. The effectiveness of antibacterial agents should be evaluated using multi-species oral biofilm models that closely mimic actual conditions. This study aimed to compare the antibacterial effects of BCSO and chlorhexidine gluconate (CHX) on oral microcosm biofilms. Biofilms using human saliva as the inoculum were cultured for 2 days and subsequently treated with 0.5% dimethyl sulfoxide, 0.5% BCSO, or 0.12% CHX once daily for 6 days. Following treatment, the red fluorescence intensity (Ratio_R/G) of the oral biofilm; biomass, including extracellular polymeric substance (EPS) levels and live bacteria counts; and colony-forming units (CFUs) of aciduric bacteria were evaluated. Ratio_R/G after BCSO treatment (1.26 ± 0.03) was not significantly different from that after CHX treatment (p = 0.552). The EPS levels were also not significantly different between the two groups (p = 0.743). The live bacteria count was 0.55 times lower in the BCSO-treated group than in the CHX-treated group (p = 0.018). No significant between-group difference was observed in the CFUs of aciduric bacteria (p = 0.935). These results suggest that BCSO exhibits antibacterial effects similar to those of CHX, highlighting its potential as an effective alternative.