Evaluation of the photodynamic efficacy and effects of haematoporphyrin monomethyl ether on Trichophyton rubrum microconidia in vitro

Background: Current available treatment modes against dermatophytoses are often tedious and sometimes unsatisfactory. As an emerging and promising approach, antimicrobial photodynamic therapy (aPDT) attracts much attention in the treatment of superficial or localised infections. Objectives: This work investigated the photodynamic efficacy and effects of haematoporphyrin monomethyl ether (HMME) on microconidia of Trichophyton rubrum in vitro. Methods: The photodynamic killing efficacy of HMME on microconidia of two T rubrum strains was assessed by MTT assay. The effects of HMME-mediated aPDT on the growth of T rubrum and cellular structure of microconidia were also investigated. Confocal laser scanning microscopy (CLSM) and flow cytometry were employed to study the intracellular localisation of HMME and generation of reactive oxygen species (ROS). Results: HMME showed no obvious toxicity in the dark, but after light irradiation it inactivated the T rubrum microconidia in a light energy dose-dependent manner, and inhibited the growth of T rubrum. CLSM demonstrated that HMME initially bound to the cell envelop and entered into the cell after light irradiation. HMME-mediated aPDT also damaged the cell cytoplasm and increased the accumulation of intracellular ROS, resulting in cell death. Conclusions: The results suggested that HMME-mediated aPDT had potential to be used in the treatment of superficial infections caused by T rubrum.