Inativação Fotodinâmica de Fungos Zoonóticos Emergentes : Sporothrix brasiliensis e Cryptococcus neoformans

Abstract

The epidemiological expansion of Sporothrix brasiliensis and Cryptococcus neoformans poses critical challenges to public health, exacerbated by systemic toxicity and resistance to conventional antifungals. Under the transdisciplinary perspective of One Health, this study evaluated the in vitro efficacy and biosafety of Photodynamic Inactivation (PDI) mediated by the photosensitizers (PS) Meso-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP), Hematoporphyrin (HP), and Rose Bengal (RB) utilizing a white LED system (total light dose of 179 J/cm²). To overcome the methodological bottleneck of hyphae persistence and viability loss in the continuous thermoconversion of S. brasiliensis, an alternating cultivation strategy was developed, intercalating cycles on PDA agar at 27 °C and thermal stimulus in BHI broth at 37 °C, which guaranteed viable and standardized yeast-phase inocula. Broth microdilution assays revealed that the tetracationic porphyrin TMPyP exhibited the highest inhibitory potential, establishing a Minimum Inhibitory Concentration (MIC) of 0.05 µM against yeastphase S. brasiliensis and inhibiting 83.63% of C. neoformans growth at 0.1 µM. On the other hand, HP exhibited selective activity against C. neoformans (MIC of 3.12 µM and an 87% reduction index - RI), whereas S. brasiliensis proved to be tolerant, probably due to its thicker cell wall (129 to 149 nm) and the electrostatic repulsion generated by the anionic character of the PS at physiological pH. RB promoted the photoinactivation of C. neoformans (MIC of 6.25 µM and 84% RI), but manifested intrinsic lipophilic toxicity in the dark against S. brasiliensis (MIC of 25 µM) and an attenuation of its cytotoxic effect under irradiation (MIC of 50 µM). The Bacterial Reverse Mutation Assay (Ames Test) with S. Typhimurium TA98 and TA100 strains confirmed the pre-clinical biosafety of the PS, keeping Mutagenicity Indices below the critical limit of 2.0. Therefore, it is concluded that PDI, especially with the use of TMPyP, consolidates itself as an effective, selective, and safe strategy for the control of these pathogens, which are considered emerging zoonotic fungi.