Susceptibility of Candida Species to Photodynamic Effects of Photofrin

Abstract

The in vitro susceptibility of pathogenic Candida species to the photodynamic effects of the clinically approved photosensitizing agent Photofrin was examined. Internalization of Photofrin by Candida was confirmed by confocal fluorescence microscopy, and the degree of uptake was dependent on incubation concentration. Uptake of Photofrin by Candida and subsequent sensitivity to irradiation was influenced by culture conditions. Photofrin uptake was poor in C. albicans blastoconidia grown in nutrient broth. However, conversion of blastoconidia to filamentous forms by incubation in defined tissue culture medium resulted in substantial Photofrin uptake. Under conditions where Photofrin was effectively taken up by Candida, irradiated organisms were damaged in a drug dose-and light-dependent manner. Uptake of Photofrin was not inhibited by azide, indicating that the mechanism of uptake was not dependent on energy provided via electron transport. Fungal damage induced by Photofrin-mediated photodynamic therapy (PDT) was determined by evaluation of metabolic activity after irradiation. A strain of C. glabrata took up Photofrin poorly and was resistant to killing after irradiation. In contrast, two different strains of C. albicans displayed comparable levels of sensitivity to PDT. Furthermore, a reference strain of C. krusei that is relatively resistant to fluconazole compared to C. albicans was equally sensitive to C. albicans at Photofrin concentrations of >3 g/ml. The results indicate that photodynamic therapy may be a useful adjunct or alternative to current anti-Candida therapeutic modalities, particularly for superficial infections on surfaces amenable to illumination.Photodynamic therapy (PDT) is a process in which cells are treated with an agent that makes them susceptible to killing by exposure to light. These agents, called photosensitizers, are generally macrocyclic compounds that exhibit no or minimal inherent toxicity but result in the generation of cytotoxic reactive oxygen species when excitation occurs with light of the appropriate wavelength. PDT has been applied most extensively in the treatment of neoplasms and shows promise as a novel therapy for some non-neoplastic disorders (4, 11). Photofrin is a photosensitizer that has been the subject of intensive investigation (4). Derived from acid treatment of hematoporphyrin, this compound has been approved by the U.S. Food and Drug Administration for the treatment of endobronchial and esophageal tumors (11) and is currently in clinical trials for several other indications.Although PDT is becoming established as a treatment modality to augment conventional chemotherapy and radiation in the oncologic literature, much less is known about the effects of photosensitizers on fungi of medical importance. Candida species have become increasingly prevalent as causes of both mucocutaneous and systemic infection in immunocompromised patients (3). Moreover, resistance of Candida to traditional antifungals such as fluconazole is increasing, with some species such as Cand...

Susceptibility of Candida albicans to photodynamic therapy in a murine model of oral candidosis

“…[17][18][19][20][21][22][23][24] The results of the present investigation demonstrated significant reduction of CFU/mL of C. albicans from tongues of mice after 400, 500, and 1000 mg/L of Photogem associated with LED light (305 J/cm 2 ) (455 and 630 nm). There is only one report describing a dose-dependent photoeradication of C. albicans in an immunodeficient murine model.…”

“…A dose-dependent inhibition of metabolic activity was observed after treatment of C. albicans strains with Photofrin (0.01 to 10 mg/L) and illumination with a light fluence of 9 J/cm 2 from an Hg arc lamp. 20 Chabrier-Roselló et al 23 also observed a dose-dependent reduction of metabolic activity of C. albicans biofilms mediated by 10 mg/L of Photofrin and with broadbrand illumination by visible light at fluences ranging from 0.9 to 18 J/cm 2 . However, it has been shown that photosensitization of Candida and subsequent susceptibility to PDT can be reduced dramatically by culture conditions, such as the type of culture medium and the presence of albumin.…”

“…However, it has been shown that photosensitization of Candida and subsequent susceptibility to PDT can be reduced dramatically by culture conditions, such as the type of culture medium and the presence of albumin. 20,37 Moreover, on epithelial surfaces C. albicans grows as a biofilm, 38 which is less susceptible to PDT than its planktonic counterpart. 24,28 It has been suggested that incomplete kill of PDT on biofilms might be because of the failure of PS and light penetration into the inner regions of the biofilm.…”

“…are susceptible to photoinactivation. [17][18][19][20][21][22][23][24] Usually, dyes (toluidine blue and methylene blue) and porphyrins are used as PS combined with red laser light. However, light sources with simpler technology and lower cost than lasers, such as light-emitting diodes (LED), have been successfully applied in PDT.…”

Susceptibility of clinical isolates of Candida to photodynamic effects of curcumin

“…For this reason, there has been an increased interest in developing PDT for local infections treatment. Different types of PS have been proposed in laboratory investigations, including porphyrins [14,15], phenothiazine dyes [16,17], chlorins [18,19], and phthalocyanines [20]. However, complete killing of the microorganisms is not frequently achieved and some of the available PS showed limited effectiveness against Candida biofilms and animal models of candidiasis [15,21].…”