The Effect of Infused Essential Oils on Manuka Honey’s Inhibition of S. mutans

This study investigated the change in antibacterial and antimicrobial effectiveness of Manuka honey when combined with eucalyptus, cardamom, and thyme essential oils against Streptococcus mutans, as well as their potential increase on Manuka honey's inhibitory effects on S. mutans compared to a control group of Manuka honey only. Manuka honey was mixed in three separate groups with a different essential oil, then used to coat a total of 120 antimicrobial discs. 30 blood agar-prepared petri dishes were then streaked with S. mutans dipped in Tryptic Soy Broth (TSB) Media. The coated antimicrobial discs were placed onto the blood agar petri dishes and incubated at 37°C. Inhibitory activity was measured through zone of inhibition (mm) after the petri dishes were incubated for twenty-four hours. Raw data indicated that thyme essential oil produced the largest average zone of inhibition, followed by eucalyptus essential oil, then the Manuka honey control, and finally the cardamom essential oil group. A one-way ANOVA was conducted to compare treatment differences between the different essential oil groups, which yielded a p-value of 0.619 (> 0.05), representing results of insignificance. These findings suggest that potential synergy between Manuka honey and herbal essential oils may be limited or dependent on factors not captured in this experiment. Overall, this study provides preliminary data toward understanding the potential of Manuka honey, particularly when interacted with herbal essential oils as a natural antibacterial option in oral health applications.