Multidrug resistance in pathogenic yeasts has been related to efflux pumps that export the drugs, therefore reducing their toxity. Some compounds (modulators) have the capacity to block these proteins. We tested 4 drugs as potential modulators fo resistance on Candida spp to fluconazole (Flu): verapamil, -estradiol and progesterone, known inhibitors of efflus pumps on human neoplastic cells. Ibuprofen has a documented fungicidal activity at high concentrations but shows at lower doses a synergistic effect with Flu mainly on resistant strains, unrelated with the fungicidal mechanism. As it is a lipophilic compound, like other modulators, we decided to study its capacity to revert resistance by blockade of efflux pumps. Material and methods: Ten clinical isolates of Candida strains resistant to Flu and 2 sensitive were incubated with sub-inhibitory concentrations of verapamil (100 ÂµM), -estradiol (50 ÂµM), progesterone (50 ÂµM) or ibuprofen (500 Âµg/ml) all from Sigma. MIC values to Flu (Pfizer) associated to each modulator were determined. Yeast cells exposed and not exposed to the modulators were stained with FUN-1 (a fluorecent probe) and analyded by FC. Results: MIC values decreased 4 to 32 times when Flu is associated with the different modulators in most strains. Only C. krusei and sensitive strains did not show significant MIC variation. The FC results showed that, on strains where MIC values to Flu were reduced by the modulators, FUN-1 staining increased, exept for C. glabrata. Conclusions: Most of the resistant strains tested seem to have efflux pumps that are blocked by the compounds used, reverting the resistant phenotype. On C. krusei the mechanism of resistance seems to be different. The FUN-1 is a useful probe that can be used to detect efflux pumps. On C. glabrata the modulators blocked the Flu transport but not the FUN-1. The hormones and especially ibuprofen, associated with Flu, might be used in the clinical management of candidosis.
Full conference title:
6th Congress of the European Confederation of Medical Mycology Societies
- ECMM 6th (2000)