FIG. 5.

Effect of pump inhibitors on the growth of C. albicans strains with decreased FLC susceptibilities in the absence and presence of FLC. (A) Inhibition of C. albicans MML606 growth in the absence (left column) or the presence (right column) of FLC (0.25× MIC) by the indicated compounds (amount per disk in parentheses)—enniatin (2 μg); peptide RC21 (6 nmol); milbemycin α20 (5 μg), α11 (5 μg), or β11 (5 μg); and disulfiram (1.2 μg)—as demonstrated by agarose disk chemosensitization assays using CSM medium (pH 7.0). (B) Chemosensitization of C. albicans strains to FLC (0.25× MIC) by enniatin (2 μg per disk) and milbemycin α20 (5 μg per disk) as demonstrated by agarose disk chemosensitization assays using CSM medium (pH 7.0). (C) Checkerboard chemosensitization of C. albicans MML606 to FLC by enniatin. Yeast cells were grown for 24 h in CSM medium pH 7.0 containing the indicated concentrations of FLC and enniatin. Growth was measured spectophotometrically as described in Materials and Methods. Each data point represents the mean of triplicate determinations from a representative experiment repeated once. Variation from the mean did not exceed 10%. (D) Inhibition by peptide RC21 of R6G efflux from C. albicans FLC-resistant strain MML611, but not from FLC-sensitive parental strain MML610. Suspensions of yeast cells of MML611 (squares) or MML610 (triangles), preloaded with R6G under glucose-deprived conditions as described in Materials and Methods, were preincubated with RC21 for 5 min at the concentrations indicated, before addition of glucose (0.4% [wt/vol] final concentration; filled symbols) or a buffer control solution (empty symbols). Each data point represents the mean of triplicate determinations in a representative experiment repeated once. Variation from the mean did not exceed 15%.