Fungicidal effect of photodynamic therapy against fluconazole-resistant Candida albicans and Candida glabrata

Abstract

SummaryAlthough photodynamic therapy (PDT) has shown great promise for the inactivation of Candida species, its effectiveness against azole-resistant pathogens remains poorly documented. This in vitro study describes the association of Photogem Ò (Photogem, Moscow, Russia) with LED (light emitting diode) light for the photoinactivation of fluconazole-resistant (FR) and American Type Culture Collection (ATCC) strains of Candida albicans and Candida glabrata. Suspensions of each Candida strain were treated with five Photogem Ò concentrations and exposed to four LED light fluences (14, 24, 34 or 50 min of illumination). After incubation (48 h at 37°C), colonies were counted (CFU ml). Single-species biofilms were generated on cellulose membrane filters, treated with 25.0 mg l )1 of Photogem Ò and illuminated at 37.5 J cm )2 . The biofilms were then disrupted and the viable yeast cells present were determined. Planktonic suspensions of FR strains were effectively killed after PDT. It was observed that the fungicidal effect of PDT was strain-dependent. Significant decreases in biofilm viability were observed for three strains of C. albicans and for two strains of C. glabrata. The results of this investigation demonstrated that although PDT was effective against Candida species, fluconazoleresistant strains showed reduced sensitivity to PDT. Moreover, single-species biofilms were less susceptible to PDT than their planktonic counterparts.

Susceptibility of clinical isolates of Candida to photodynamic effects of curcumin

“…The level of variation within the same species was more pronounced in the planktonic cultures exposed to PDT, but biofilms also showed significant discrepancies. Significant differences observed in the present study among Candida species and strains with regard PDT susceptibility also concur with previous studies [15,32,39]. Therefore this investigation once again confirms the importance of testing more than one isolate of Candida belonging to a given species to characterize the species-specific behavior.…”

“…C. glabrata required a higher CUR concentration to achieve 4 log reduction in CFU/ml counts and it was not completely inactivated in any of the protocols tested. Other investigations also found the reduced susceptibility of C. glabrata suspensions to photoinactivation [14,15]. However, this reduced susceptibility was not observed in C. glabrata biofilms, which showed similar levels of photoinactivation in comparison with C. albicans biofilms.…”

“…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].…”

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

“…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. 39,40 Thus, in comparison with these in vitro studies, the higher PS concentrations and light fluence required for photoinactivation in the present investigation may be explained by the physiological responses of C. albicans to the in vivo environment.…”

“…A previous in vitro study showed that PDT mediated by Photogem and blue LED light resulted in complete inactivation of planktonic suspensions and significant reduction in biofilm viability. 28 However, in vivo application of antimicrobial PDT using porphyrins and LED light has not yet been well established and animal models may provide outcomes more closely correlated to clinical situations. Thus, the aim of the present investigation was to contribute to in vivo antimicrobial PDT development by reporting on the photoinactivation of C. albicans in a murine model of oral candidosis using a porphyrin in association with LED light sources of different wavelengths.…”