Candida strains biofilm production and susceptibility to photosensitizer agent toluidine blue-O

RAMADÁN, S., ; DALMASO, H., ; LÓPEZ, C., ; BULACIO, L..; POSTIGO, A.,; SORTINO, M.

Congreso; XVI Congreso y XXXIV Reunión anual Sociedad Biología de Rosario; 2014

Photodynamic therapy has emerged for the treatment of infections produced by microbial pathogens, including them capables of forming biofilms.The objective of this work was to study the biofilm production by different Candida strains and the effect of photodynamic therapy with Toluidine Blue O (TBO) over them. Twenty Candida strains were isolated as causative of oropharyngeal candidiasis (C. albicans N=8, C. tropicalis N=4, C. parapsilosis N=5, C. krusei N=2, C. glabrata N=1). In the first stage, quantitative biofilm measurement was performed in a 96-well microtiter plate. Briefly, yeast were grown and incubated for 24 h at room temperature, then cultures were poured out, washed and stained with crystal violet solution. After solubilization with ethanol-acetone, OD595 nm was determined. Strains were noted as strong biofilm producers when OD ≥ 0,24; strains with OD between 0,12 and 0,24 were designated as moderate producers and those with OD < 0,12 as no producers. In the second stage, antifungal photosensitive activity against biofims were determined by the Clinical and Laboratory Standards broth microdilution technique (M27-A3). TBO photosensitizer agent was evaluated at a final concentration of 500μg/ml and was irradiated for 60 min. Results showed that 50% of strains were biofilm producers (25% were strong producers and 25%, moderate producers). TBO showed no antifungal photosensitive activity against biofilms.