Fungicidal efficacy of photodynamic therapy using methylene blue against Sporothrix globosa in vivo and in vivo

Sporothrix schenckii strains are the aetiological agents of sporotrichosis, which is endemic in China. The most common clinical manifestation of sporotrichosis is cutaneous and subcutaneous nodular lesions with lymphangitis involvement. Currently, antifungal therapy is commonly used to treat sporotrichosis, however, drug resistance and complications are the major concerns, especially in patients who have asymptomatic liver injury or existing liver disorders, children, and pregnant women. To assess the in vitro and in vivo antifungal efficacy of photodynamic therapy (PDT) using photosensitizer methylene blue against Sporothrix strains isolated from patients. A light-emitting diode (LED) lamp was used as the light source with a wavelength of 640 ± 10 nm. For the in vitro study, the presence of five Sporothrix strains was assayed following LED irradiation with and without photosensitizer (L + M + , L + M-), with photosensitizer alone (L-M + ), or no exposure to LED light or photosensitizer (L-M-). For the in vivo study, mice were infected with the fungi and then treated with sodium chloride (control group), antifungal itraconazole alone (itraconazole group), and a combination of antifungal itraconazole and PDT (itraconazole +PDT group), or PDT alone (PDT group). The results showed that, in vitro, PDT (L + M + ) effectively inhibited fungal growth at an energy density of 40 J/cm2. In vivo, itraconazole + PDT effectively inhibited growth of the fungus with the highest level of efficacy. PDT with methylene blue is an effective adjuvant therapy for resistant infections of Sporothrix.