Photodynamic inactivation of different Candida species and inhibition of biofilm formation induced by water-soluble porphyrins.

BACKGROUND

Candida spp. is the main fungal genus related to infections in humans, and its treatment has become a challenge due to the production of biofilm and its resistance/multi-resistance profile to conventional antifungals. Antimicrobial photodynamic therapy stands out as a treatment characterized by a broad spectrum of antimicrobial action, being able to induce oxidative stress in pathogens, and porphyrins are photosensitizers with high selectivity to pathogens. Thus, this work aimed to analyze the photoinactivation of different species of Candida by two cationic (4-HTMeP and 3-HTMeP) and one anionic (4-HTPSP) porphyrins.

MATERIALS AND METHODS

Microdilution assays were performed to determine the MIC, with subsequent determination of MFC. Determination of oxidative species was done through the use of scavengers, while biofilm morphological features were investigated using the atomic force microscopy.

RESULTS

Cationic porphyrins were significantly efficient in inactivating Candida albicans and non-albicans species with 100% growth inhibition and fungicidal activity (MFC/MIC ≤ 4.0). The cationic porphyrins were also able to interfere in Candida spp biofilm formation. The photo-oxidative mechanism activated by 3-HTMeP in Candida spp. is concurrent with the production of singlet oxygen and oxygen radical species. In the AFM analysis, 3-HTMeP was able to reduce yeast adhesion to the surface.

CONCLUSIONS

Cationic porphyrins can photo-inactivate different species of Candida in both planktonic and biofilm-associated forms, and reduce the adhesion of these fungi to the surface.