Cell Viability of Candida albicans Against the Antifungal Activity of Thymol

Candida albicans is a commensal fungus, but circumstantially it may cause superficial infections of the mucous membranes, such as denture stomatitis, when a biofilm is formed on the surface of dental prostheses. This study evaluated the cell viability of C. albicans biofilms against the antifungal activity of thymol when compared with miconazole, by the fluorescence imaging using SYTO 9 and propidium iodide dyes, and counting of colony forming units. C. albicans standard strains (ATCC 11006) were used. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of drugs were determined by broth microdilution tests and the inoculum was standardized to match 0.5 on the McFarland scale (106 cfu/mL). Biofilms were grown on the surface of acrylic resin disks in parallel flow chambers from Sabouraud broth supplemented with 10% dextrose. For counting of colony forming units, the fungal solution was sequentially diluted and plated in Sabouraud dextrose agar. Data were analyzed using two-way ANOVA and Tukey's test (a=5%). Biofilms treated with thymol and miconazole presented low numbers of viable cells at the evaluated exposure times. There was statistically significant difference (p0.05). In conclusion, both drugs have similar efficiency as antifungal agents against biofilms of C. albicans formed on acrylic surfaces. Candida albicans é um fungo comensal que circunstancialmente pode causar infecções superficiais das mucosas, como a estomatite protética, na qual o biofilme se forma sobre a superfície das próteses dentárias. Este estudo avaliou a viabilidade celular de biofilmes de C. albicans frente à ação antifúngica do timol em comparação com o miconazol por meio da técnica de fluorescência, empregando os corantes SYTO 9 e iodeto de propídio, e contagem das unidades formadoras de colônia. Utilizaram-se cepas de C. albicans (ATCC 11006). As concentrações inibitórias mínimas (CIM) e fungicidas mínimas (CFM) das drogas foram determinadas com testes de microdiluição em caldo, sendo o inóculo padronizado para corresponder a 0,5 da escala de McFarland (106 UFC/mL). Os biofilmes foram cultivados sobre a superfície de discos de resina acrílica, em células paralelas de fluxo, a partir de caldo Sabouraud suplementado com dextrose 10%. Para a contagem das unidades formadoras de colônia, as soluções fúngicas foram