title: Photodynamic inactivation of conidia of the fungi Metarhizium anisopliae and Aspergillus nidulans with methylene blue and toluidine blue.
abstract: Antimicrobial photodynamic treatment (PDT) is a promising method that can be used to control localized mycoses or kill fungi in the environment. A major objective of the current study was to compare the conidial photosensitization of two fungal species (Metarhizium anisopliae and Aspergillus nidulans) with methylene blue (MB) and toluidine blue (TBO) under different incubation and light conditions. Parameters examined were media, photosensitizer (PS) concentration and light source. PDT with MB and TBO resulted in an incomplete inactivation of the conidia of both fungal species. Conidial inactivation reached up to 99.7%, but none of the treatments was sufficient to achieve a 100% fungicidal effect using either MB or TBO. PDT delayed the germination of the surviving conidia. Washing the conidia to remove unbound PS before light exposure drastically reduced the photosensitization of A. nidulans. The reduction was much smaller in M. anisopliae conidia, indicating that the conidia of the two species interact differently with MB and TBO. Conidia of green and yellow M. anisopliae mutants were less affected by PDT than mutants with white and violet conidia. In contrast to what occurred in PBS, photosensitization of M. anisopliae and A. nidulans conidia was not observed when PDT was performed in potato dextrose media.
authors.affiliation: Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Fernanda P
authors.initials: FP
authors.lastname: Gonzales
authors.forename: Sérgio H
authors.initials: SH
authors.lastname: da Silva
authors.forename: Donald W
authors.initials: DW
authors.lastname: Roberts
authors.forename: Gilberto U L
authors.initials: GU
authors.lastname: Braga
mesh_terms: D001233:Aspergillus nidulans / Q000166:cytology / Q000528:radiation effects*; D003116:Color; D004203:Disinfection / Q000379:methods*; D052981:Metarhizium / Q000166:cytology / Q000528:radiation effects*; D008751:Methylene Blue / Q000494:pharmacology*; D009154:Mutation; D010778:Photochemotherapy / Q000379:methods; D017319:Photosensitizing Agents / Q000494:pharmacology; D013172:Spores, Fungal / Q000235:genetics / Q000528:radiation effects*; D014048:Tolonium Chloride / Q000494:pharmacology*
chemical_list: D017319:Photosensitizing Agents; D014048:Tolonium Chloride; D008751:Methylene Blue