Miconazole activity against Candida biofilms developed on acrylic discs.

Oral candidiasis in the form of Candida-associated denture stomatitis (CaDS) is associated with Candida adhesion and biofilm formation on the fitting surface of poly (methyl methacrylate) (PMMA) dentures. Candida biofilms show considerable resistance to most conventional antifungal agents, a phenomenon that is considered a developmental-phase-specific event that may help explain the high recurrence rates associated with CaDS. The aim of this study was to examine the activity of miconazole towards in vitro-grown mature Candida biofilms formed on heat-cured PMMA discs as a standardized model. The effect of miconazole nitrate on Candida biofilms developed on acrylic discs was determined for C. albicans MYA-2732 (ATCC), C. glabrata MYA-275 (ATCC), and clinical isolates, C. albicans 6122/06, C. glabrata 7531/06, C. tropicalis 8122/06, and C. parapsilosis 11375/07. Candida biofilms were developed on heat-cured poly(methyl methacrylate) discs and treated with miconazole (0.5 - 96 μg/ml). The metabolic activity of the biofilms was measured by the XTT reduction assay. The minimum inhibitory concentrations (MICs) of miconazole against Candida species were determined by the microdilution method. The MICs for miconazole for the investigated strains ranged from 0.016-32 μg/ml. Treatment with miconazole resulted in a significant reduction of biofilm metabolic activity for all strains. The highest inhibition was observed at 96 μg/ml miconazole. In the case of C. glabrata MYA-275 and C. tropicalis 8122/06 this corresponded to 83.7% and 75.4% inhibition, respectively. The lowest reduction was observed for C. parapsilosis 11375/07-46.1%. For all Candida strains there was a strong correlation between MIC values and miconazole concentrations corresponding to a reduction of metabolic activity of the biofilm by 50%. Miconazole exhibits high antifungal activity against Candida biofilms developed on the surface of PMMA discs. The study provides support for the use of miconazole as an effective agent for the treatment of CaDS.