Inhibitory Effects of Photodynamic Inactivation on Planktonic Cells and Biofilms of Candida auris

Candida auris is an emerging pathogen that has caused numerous severe infections in recent years, and has therefore become a global concern for public health agencies. Most conventional antifungal agents, especially fluconazole, have shown limited effects on this pathogen. New methods to restrict this pathogen are in urgent demand. Antimicrobial photodynamic therapy (aPDT) has been shown to be a promising technique against multiple pathogenic fungi. This study sought to determine the in vitro effect of aPDT using methylene blue (MB) combined with light-emitting diode (LED) on the viability of planktonic cells and biofilms of five clinical strains of C. auris . MB (8, 16 and 32 μg/ml) was applied as the photosensitizer, and a LED (635 nm, 12 and 24 J/cm 2 ) device was used as light source to activate the photosensitizer. The results showed that there was no growth of tested C. auris strains following aPDT on planktonic cultures. In addition, aPDT exhibited colony-forming unit reduction of up to 7.20 log 10 against C. auris biofilms. These data demonstrate that in vitro aPDT with MB and LED offers promising potential for the treatment of C. auris infections.