Effects of Photodynamic Therapy on Standard And Fluconazole-Resistant Candida Albicans Strains: An In Vitro Study

Objective: The extensive and repetitive use of antifungal drugs has led to resistance from Candida albicans. Photodynamic therapy (PDT) is an emerging and promising approach for combating drugresistant microbes. The aim of this study was to evaluate photosensitization effects of 810-nm and 670- nm diode lasers against standard suspension of fluconazole-resistant (TS) and susceptible (ATCC90028) C.albicans considering optimum duration of laser irradiation. Materials and Methods: In this in vitro study, suspensions of two kinds of C. albicans were prepared, transferred to 96-holes plates and exposed to 810-nm (500mW, CW) and 670-nm (Periowave®, 200 mW) diode lasers in the presence or absence of methylene blue (MB). 100-fold dilution of the suspension was plated on Sabouraud Dextrose Agar (SDA) and the colony-forming units (CFU) were counted after 24h of incubation at 37°C. During irradiation, an infrared thermometer was used to measure the temperature in the experimental well. Also, the morphology of C.albicans was observed microscopically. Results: With MB, both TS and ATCC90028 could be effectively inactivated by 670-nm and 810-nm diode lasers. The antifungal effect of the 670-nm diode laser was almost 100% for 377s; that of the 810- nm laser was 75% for 754s. Within irradiation time 0–390s, the temperature of the fungal suspension changed by <2°C. The laser exposure could not change the drug resistance of the fluconazole-resistant C. albicans. Microscope images suggested that PDT induced C.albicans cells expansion and lysis. Conclusion: PDT using the two types of lasers had excellent sterilization effect on fluconazole-resistant and susceptible C.albicans.