In vitro inhibition of a multispecies oral cavity biofilm by Syzygium aromaticum essential oil

Objective To evaluate the anti‐fungal activity of Syzygium aromaticum essential oil and its inhibition of a multispecies biofilm in patients with oral candidiasis. Background Inhibiting biofilm formation on the denture surface is an important practice for preventing denture stomatitis. Materials and Methods The anti‐fungal activity against Candida albicans and non‐albicans Candida species was evaluated through the microdilution method to define Minimal Inhibitory (MIC) and Fungicidal (MFC) Concentrations. Time‐kill assay assessed growth kinetics of C. albicans based on pre‐determined time points (0, 1, 2, 4, 6 and 24 hours). A multi‐species biofilm was formed using human saliva from patients with oral candidiasis and anti‐biofilm activity determined by Colony Forming Units per milliliter (CFU/mL) count, fluorescence microscopy with calcofluor white to observe yeast presence and structure, and metabolic activity by XTT (2,3‐Bis‐(2Methoxy‐4‐Nitro‐5‐Sulfophenyl)‐2H‐Tetrazolium‐5‐carboxanilide) reduction assay. Results The essential oil showed an anti‐fungal activity against all Candida species (MIC 500‐1000 µg/mL, MFC 1000‐2000 µg/mL), and the time‐kill assay showed that 2000 µg/mL (from 2 hours onward) and 1000 µg/mL (from 4 hours onward) concentrations had substantially lower yeast growth than the negative control. In the biofilm analysis, the essential oil had a lower CFU/mL count and a biofilm metabolic activity (91.4%) than seen with its negative control, and in both analyses, the essential oil was not significantly different from the positive control (chlorhexidine). Morphological analysis showed amorphous and fragmented cellular structures after treatment with the essential oil. Conclusion Syzygium aromaticum essential oil had anti‐fungal activities, reduced the Candida growth kinetics substantially and inhibited the multi‐species biofilm formation.