Fig. 6
Effect of Origanum vulgare essential oil combined with fluconazole and nystatin on the viability of biofilms. The effects of the combination of O-EO with fluconazole (upper row) and nystatin (lower row) on cell viability were measured using the MTT reduction assay in two C. albicans strains: ATCC 90029 (left panels) and ATCC 10231 (right panels). Preformed biofilms (24 h) were exposed to the different drugs for 24 h. Seven concentrations were mixed in every possible combination to obtain an effect matrix plotted with the Combenefit software. The graphs at the left of each panel represent a XYZ model of the combination and is analyzed according to Loewe’s model of drug additivity. At the right of each graph is the matrix of combinations that shows the differences between the theoretical combinations and empirical data by a number generated for each point. Positive numbers are given for synergistic combinations, whereas negative numbers indicate antagonism. Color code indicates statistical significance of the difference between theorical and empirical model (Student’s t-test). *p < 0.05. The graphs show the mean ± standard deviation of three independent experiments