TABLE 1.
Synergistic effect of fluconazole with CATEQ, QUERC, and EPIG against strains of Candida tropicalis resistant to fluconazole
| C. tropicalis straina | MIC50 (μg/ml)b |
FLC-FLAV interaction |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Standardc |
Combinationd |
FICI |
Interpretatione | ||||||
| FLC | CATEQ, QUERC, and EPIG | CATEQ + FLC 16 | QUERC + FLC 16 | EPIG + FLC 16e | CATEQ + FLC | FICI QUERC + FLC | FICI EPIG + FLC | ||
| 1 | 64 | >128 | 16 | 0.50 | 0.50 | 0.38 | 0.25 | 0.25 | SYN |
| 2 | 64 | >128 | <0.25 | <0.25 | <0.25 | 0.25 | 0.25 | 0.25 | SYN |
| 3 | 64 | >128 | <0.25 | <0.25 | 1.0 | 0.25 | 0.25 | 0.26 | SYN |
| 4 | 64 | >128 | 0.25 | 0.25 | 0.50 | 0.25 | 0.25 | 0.25 | SYN |
| 5 | 64 | >128 | 0.25 | 0.25 | <0.25 | 0.25 | 0.25 | 0.25 | SYN |
| 6 | 64 | >128 | 0.25 | <0.25 | <0.25 | 0.25 | 0.25 | 0.25 | SYN |
Yeasts isolated from biological samples.
FLC, fluconazole. The MIC50 value was defined as the lowest concentration that produced a 50% reduction in the growth of fungal cells after a 24-h incubation.
The procedure was performed according to the CLSI M27-A3 2008 protocol (23). Fluconazole concentrations ranged from 64 to 0.125 mg/liter, and flavonoid concentrations varied from 128 to 0.25 mg/liter.
The concentration of fluconazole was fixed at 16 mg/liter (FLC 16), and the flavonoid concentrations varied from 128 to 0.25 mg/liter. The synergistic effect of fluconazole and flavonoids was calculated on the basis of the FICI, which is equal to ([FLC]/[CFS]) + ([FLAC]/CFlaS), where [FLC] and [FLAC] are the concentrations of fluconazole and flavonoids that showed activity when combined, respectively, and [CFS] and [CFlaS] are the concentrations of these drugs with activities in isolation, respectively.
Interpretation was performed according to the value of FICI. An FICI of <0.5 is synergism (SYN), 0.5 < FICI ≤ 4.0 is indifference (IND), and an FICI of >4.0 is antagonism (ANT).