Photodynamic inactivation of clinical isolates of Candida using Photodithazine^®

Abstract

This study evaluated the photodynamic inactivation (PDI) mediated by Photodithazine^® (PDZ) against 15 clinical isolates of Candida albicans, Candida glabrata and Candida tropicalis. Each isolate, in planktonic and biofilm form, was exposed to PDI by assessing a range of PDZ concentrations and light emitting diode fluences. Cell survival of the planktonic suspensions was determined by colony forming units (CFU ml⁻¹). The antifungal effects of PDI against biofilms were evaluated by CFU ml⁻¹ and metabolic assay. Data were analyzed by non-parametric tests (α = 0.05). Regardless of the species, PDI promoted a significant viability reduction of planktonic yeasts. The highest reduction in cell viability of the biofilms was equivalent to 0.9 log₁₀ (CFU ml⁻¹) for C. albicans, while 1.4 and 1.5 log₁₀ reductions were obtained for C. tropicalis and C. glabrata, respectively. PDI reduced the metabolic activity of biofilms by 62.1, 76.0, and 76.9% for C. albicans, C. tropicalis, and C. glabrata, respectively. PDZ-mediated PDI promoted significant reduction in the viability of Candida isolates.

Keywords:

• photodynamic therapy
• Candida spp.
• biofilms

Acknowledgments

The authors thank Olympio Teixeira Neto for help with the statistical analysis of the data. This work was supported by grants 2008/00601-6, 2008/03994-9, and 1998/14270-8 (CEPID Program), São Paulo Research Foundation (FAPESP).