The effects of rose bengal- and erythrosine-mediated photodynamic therapy on Candida albicans Anna Carolina Borges Pereira Costa, Vanessa Maria Campos Rasteiro, Cristiane Aparecida Pereira, Rodnei Dennis Rossoni, Juliana Campos Junqueira and Antonio Olavo Cardoso Jorge Department of Biosciences and Oral Diagnosis, School of Dentistry of Sa ˜o Jose ´ dos Campos, UNESP – Univ Estadual Paulista, Sa ˜o Jose ´ dos Campos, SP, Brazil Summary The aim of this study was to evaluate the effects of photodynamic therapy (PDT) using rose bengal or erythrosine with light emitting diode (LED) on Candida albicans planktonic cultures and biofilms. Seven C. albicans clinical strains and one standard strain (ATCC 18804) were used. Planktonic cultures and biofilms of each C. albicans strain were submitted to the following experimental conditions: (a) treatment with rose bengal and LED (RB+L+); (b) treatment with erythrosine and LED (E+L+); and (c) control group, without LED irradiation or photosensitiser treatment (P)L)). After irradiation of the planktonic cultures and biofilms, the cultures were seeded onto Sabouraud dextrose agar (37 °C at 48 h) for counting of colony-forming units (CFU ml )1 ) followed by posterior ANOVA and TukeyÕs test analyses (P < 0.05). The biofilms were analysed using scanning electron microscopy (SEM). The results revealed a significant reduction of planktonic cultures (3.45 log 10 and 1.97 log 10 ) and of biofilms (<1 log 10 ) for cultures that were subjected to PDT mediated using either erythrosine or rose bengal, respectively. The SEM data revealed that the PDT was effective in reducing and destroying of C. albicans blastoconidia and hyphae. The results show that erythrosine- and rose bengal-mediated PDT with LED irradiation is effective in treating C. albicans. Key words: Candida albicans, erythrosine, rose bengal, light emitting diode, photodynamic therapy, biofilm. Introduction Oral candidiasis is an opportunistic infection caused by yeast of the Candida genus, primarily Candida albicans. It is generally associated with predisposing factors such as the use of immunosuppressive agents, antibiotics or oestrogens. 1 This disease is characterised by the pres- ence of a biofilm formed by a heterogeneous mixture of blastoconidia, pseudohyphae and hyphae residing among extracellular polymeric substances (EPS). 2 Candida biofilms exhibit high levels of resistance against disinfectants and antifungal agents. 3,4 Studies that have evaluated the effects of different concentra- tions of medicines on biofilms have demonstrated that increases in antifungal resistance are associated with progression through the several stages of biofilm formation. 5,6 The reduction in susceptibility of Candida spp. strains to antifungal agents due to the increase in survival of immunosuppressed patients and the over-use of antimicrobial drugs has resulted in an interest in the development of new therapeutic strategies. 7 Photodynamic therapy (PDT) has been used for the treatment of cancer and localised bacteria, fungus, virus and protozoan infections as well as in the sterilisation of blood, water and food. The mechanism of this treatment is based on the irradiation of a light-sensitive non-toxic agent; upon irradiation of the dye with visible light of a suitable wavelength, reactive oxygen species such as free radicals and singlet oxygen are produced. 8 Light emitting diodes (LED) have been described as a promising light source for use in place of lasers, because they are characterised by wider emission bands, are Correspondence: A. C. B. P. Costa, Department of Biosciences and Oral Diagnosis, School of Dentistry of Sa ˜ o Jose ´ dos Campos, UNESP – Univ Estadual Paulista, Engenheiro Francisco Jose ´ Longo 777, Sa ˜ o Dimas, Sa ˜o Jose ´ dos Campos, CEP 12245-000, SP, Brazil. Tel.: +55 12 3947 9033, Fax: +55 12 3947 9010. E-mail: carol_biolog@yahoo.com.br Accepted for publication 17 March 2011 Original article doi:10.1111/j.1439-0507.2011.02042.x Ó 2011 Blackwell Verlag GmbH • Mycoses 55, 56–63 mycoses Diagnosis,Therapy and Prophylaxis of Fungal Diseases