Antimicrobial photodynamic therapy as a new approach for the treatment of vulvovaginal candidiasis: preliminary results

In this work, we present the efficacy of photodynamic therapy against yeast cells in an animal model. We tested two photosensitizers, methylene blue and protoporphyrin IX. Thirty-seven female BALB-c mice with a body mass of 20-25 g were used. To achieve persistent vaginitis, estrus was induced by subcutaneous injection of 0.1 mg/mL estradiol valerate applied weekly. Three days after pseudo-estrus, intravaginal inoculation with Candida albicans was performed. Mice were anesthetized with ketamine (80 mg/kg) and xylazine (10 mg/kg) by intraperitoneal injection before inoculation, and antimicrobial photodynamic therapy (aPDT) was performed 5 days after fungal inoculation. Two photosensitizers were tested, methylene blue (MB; 100 μM) and protoporphyrin IX (PpNetNI; 10 μM). Two custom-made LEDs emitting light at 660 and 630 nm at approximately 800 mW each were used for irradiation. The aPDT treatment reduced the fungal colony-forming units (CFUs) by one order of magnitude for the MB (p = 0.020) and PpNetNI (p = 0.018) photosensitizers. Seven days after the treatment, there were significantly fewer CFUs compared to the control group (p = 0.041 and p = 0.035 for MB and PpNetNI, respectively), but this was not increased compared to the initial number immediately after aPDT. Using aPDT as a therapeutic option to decrease fungal infection in a vaginal candidiasis model resulted in a significant reduction in the C. albicans population. Both photosensitizers were effective for preventing reinfection within 7 days. The aPDT also had no effect on the vaginal mucosa at the ultrastructural level. In addition to the fungicide effect, we observed reduced swelling and lack of the formation of abscesses, microabscesses coating the cornified epithelial layer, and the accumulation of neutrophils in the submucosa.