Fungistatic effects of optical brightener 220 against Trichophyton tonsurans, Aspergillus fumigatus and Candida albicans.

Background: Dermatophytes are one of the main causes of dermal infections. Moreover, there are some opportunistic fungi such as Aspergillus fumigatus (mycelial form) and Candida albicans (yeasty form) that in immunosuppressed patients can cause cutaneous disease. Objectives: The possible effect of optical brightener 220 (OB-220) on the growth of fungi has been evaluated in this study. Methods: Isolates were grown on agar plates containing OB-220 in concentration between 0.06 and 11.68 mg ml-1. MICs of OB-220, ketoconazole and fluconazole were obtained by the agar dilution method. Hyphae and yeasts grown with OB-220 were compared with controls by fluorescence and transmission electron microscopy. The cell cytotoxicity of OB-220 was also assessed. Results: The MIC90 of OB-220 was obtained: 1.17-1.46 mg ml-1 for A. fumigatus, 0.58-1.17 mg ml-1 for C. albicans and 0.29 mg ml-1 for Trichophyton tonsurans. Electron microscopy revealed a thickening and blurred contours of the cell wall by OB-220. OB-220 in concentrations up to 11.68 mg ml-1 posed no mammalian cell toxicity. Conclusion: OB-220 suppresses the growth of fungi by interfering with the formation of normal chitin.