The rise of Candida spp. resistant to classic triazole antifungal agents has led to a search for new therapeutic options. Here, we evaluated combinations of antifungals in a checkerboard assay against two groups of Candida glabrata strains: one containing fluconazole-susceptible clinical isolates (FS) and another containing fluconazole-resistant laboratory derivative (FR). The most synergistic combination observed was amphotericin B + flucytosine (synergistic for 61.77 % of FS strains and 76.47 % of FR strains). The most antagonistic combination observed was ketoconazole + flucytosine (FS 61.77 % and FR 55.88 %). Surprisingly, most combinations evidenced indifferent interactions, and the best synergism appeared when amphotericin B and flucytosine were combined against both groups of isolates.

The extensive use of azole antifungal agents has promoted the resistance of Candida spp to these drugs. Candida glabrata is a problematic yeast because it presents a high degree of primary or secondary resistance to fluconazole. In Brazil, C. glabrata has been less studied than other species. In this paper, we compared the activity of three major classes of antifungal agents (azoles, echinocandins and polyenes) against fluconazole-susceptible (FS) and fluconazole-resistant (FR) C. glabrata strains. Cross-resistance between fluconazole and voriconazole was remarkable. Among the antifungal agents, the echinocandins were the most effective against FS and FR C. glabrata and micafungin showed the lowest minimal inhibitory concentrations

Introduction: This study evaluated the susceptibilities of oral candidiasis-derived Candida albicans, fluconazole-resistant (FR) Candida dubliniensis, and fluconazole-susceptible (FS) C. dubliniensis to synthetic antiseptics [chlorhexidine gluconate (CHX), cetylpyridinium chloride (CPC), and triclosan (TRC)] and natural compounds (carvacrol, eugenol and thymol). Methods: Susceptibility tests were performed based on the M27-A3 reference method. The fluconazole-resistant C. dubliniensis strains were obtained after prolonged in vitro exposure to increasing fluconazole concentrations. The geometric mean values for minimum inhibitory concentrations and minimum fungicidal concentrations were compared among the groups. Results: FS C. dubliniensis was more sensitive to CPC and TRC than FR C. dubliniensis and C. albicans. However, eugenol and thymol were more active against FR C. dubliniensis. The fungicidal activities of CHX and TRC were similar for the three groups, and FR C. dubliniensis and C. albicans had similar sensitivities to CPC. Conclusions: The resistance of C. dubliniensis to fluconazole affects its sensitivity to the synthetic antiseptics and natural compounds that were tested.