Methods: EO anticandidal activity was screened via the agar disk diffusion method. Then, minimum inhibitory concentrations (MIC) and minimum cidal concentrations (MCC) were determined via the microbroth dilution method. Finally, sessile MIC (sMIC) was determined on biofilm in adhesion and biofilm modes using the XTT reduction assay.
Results: At both 5% and 10% concentrations, 7 of 14 EOs (cinnamon bark, Thai basil leaf, orange peel, spearmint leaf, lemon peel, fennel leaf and kaffir lime leaf) showed inhibition zones ranging from 7-64 mm. MIC values ranged from 0.049 to 6.250 μL/mL. MCC values ranged from 0.098 to 6.250 μL/mL. Cinnamon bark and thai basil leaf EOs had the lowest planktonic MIC and MCC values. sMIC was then determined in adhesion and biofilm mode for these two EOs. For cinnamon bark in adhesion mode, the sMIC50 and sMIC90 were 0.049 and 0.195 μL/mL, respectively. In biofilm mode, the sMIC50 and sMIC90 for cinnamon bark were 0.098 and 0.781 μL/mL, respectively. For Thai basil in adhesion mode, the the sMIC50 and sMIC90 were 0.391 and 1.563 μL/mL, respectively. In biofilm mode, the sMIC50 and sMIC90 for Thai basil were 0.781 and 6.250 μL/mL, respectively.
Conclusions: Planktonic MIC and MCC, and sessile MIC in adhesion and biofilm modes for the essential oils made from cinnamon bark Thai basil leaves exhibited the most impressive anticandidal activity.