5-Aminolevulinic acid-mediated photodynamic therapy has effective antifungal activity against Sporothrix globosa in vitro.

BACKGROUND

An alternative therapy for sporotrichosis is necessary to reduce the treatment time and raise clinical efficacy. The 5-Aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) is a promising platform with which to treat mycoses. However, despite the worldwide prevalence of Sporothrix globosa, a causative agent of sporotrichosis, the effect of ALA-PDT on this pathogen has not been validated.

OBJECTIVES

The aim of this study was to evaluate the effect of ALA-PDT on S globosa and the protection of melanin through an in vitro study. The mechanisms involved were also investigated.

METHODS

To estimate the survival rate of S globosa treated with ALA-PDT and the protection offered by melanin, the conidia and yeast cells of wild-type S globosa (Mel+), other clinical strains, tricyclazole-treated Mel+ and an albino mutant strain (Mel-) were incubated with and without ALA or irradiation. Reactive oxygen species generation by Mel+ conidia induced by ALA-PDT was assayed. SEM and TEM were conducted to obverse ultrastructural changes in the conidia. A comet assay was performed to evaluate DNA damage.

RESULTS

The survival rate of S globosa conidia and yeast cells significantly decreased following incubation with 1.19M ALA and 162 J/cm2 irradiation in vitro. Melanin was not only capable of protecting the conidia against ALA-PDT, but also against ALA or irradiation alone. After induction by ALA-PDT, alterations in reactive oxygen species generation, DNA damage and ultrastructural changes were observed.

CONCLUSIONS

ALA-PDT inhibits the survival of S globosa conidia in vitro and therefore has potential for the treatment of sporotrichosis.