Investigation of the additive antimicrobial effects of clove and marjoram extracts against common oral pathogens

According to traditional Persian medicine, clove and marjoram have antibacterial properties. This study investigates their potential synergistic effects against oral pathogens. Ethanol extracts of clove and marjoram were tested for antimicrobial activity against Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguinis, and Candida albicans using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), time-kill assays, and fractional inhibitory concentration (FIC) indices. Clove extract demonstrated superior activity, with MIC/MBC values of 0.52/1 mg/mL for S. mutans, 0.2/1 mg/mL for S. salivarius and S. sanguinis, and 4/8 mg/mL for C. albicans, outperforming metronidazole and Persica. Marjoram extract also showed notable activity, especially against S. salivarius (MIC/MBC: 0.52/2.15 mg/mL). FIC analysis revealed additive effects for clove-marjoram combinations against S. mutans, S. sanguinis, and C. albicans, though a reducing effect was observed for S. salivarius. Time-kill studies confirmed enhanced bactericidal effects at 24 hours compared to reference treatments. The additive effects of clove and marjoram extracts show promise as supplementary agents to existing antimicrobial products. Further research is needed to evaluate their safety and efficacy in vivo.