In Vitro Effect of Photodynamic Therapy with Different Lights and Combined or Uncombined with Chlorhexidine on Candida spp.

Vanesa Pérez-Laguna,Yolanda Gilaberte,Antonio Rezusta,Yolanda Barrena-López

doi:10.3390/pharmaceutics13081176

Abstract

Candidiasis is very common and complicated to treat in some cases due to increased resistance to antifungals. Antimicrobial photodynamic therapy (aPDT) is a promising alternative treatment. It is based on the principle that light of a specific wavelength activates a photosensitizer molecule resulting in the generation of reactive oxygen species that are able to kill pathogens. The aim here is the in vitro photoinactivation of three strains of Candida spp., Candida albicans ATCC 10231, Candida parapsilosis ATCC 22019 and Candida krusei ATCC 6258, using aPDT with different sources of irradiation and the photosensitizer methylene blue (MB), alone or in combination with chlorhexidine (CHX). Irradiation was carried out at a fluence of 18 J/cm2 with a light-emitting diode (LED) lamp emitting in red (625 nm) or a white metal halide lamp (WMH) that emits at broad-spectrum white light (420–700 nm). After the photodynamic treatment, the antimicrobial effect is evaluated by counting colony forming units (CFU). MB-aPDT produces a 6 log10 reduction in the number of CFU/100 μL of Candida spp., and the combination with CHX enhances the effect of photoinactivation (effect achieved with lower concentration of MB). Both lamps have similar efficiencies, but the WMH lamp is slightly more efficient. This work opens the doors to a possible clinical application of the combination for resistant or persistent forms of Candida infections.

Highlights

Candida spp. are commensal fungal species commonly colonizing human mucosal and skin surfaces, but they may become pathogenic in some particular scenarios such as treatment with antibiotics, immunocompromised patients, etc., producing in these cases infections that range from superficial to severe skin and mucosal lesions, to even systemic invasion at its worst degree [1]
As a source of irradiation, we use a light-emitting diode (LED) lamp emitting in red or a white metal halide lamp (WMH) that emits at broad-spectrum white light which is comparable to the emission spectrum of daylight
The minimum concentration of methylene blue (MB) required to achieve this effect was 320 μg/mL in all cases except in those irradiated with a WMH lamp in C. parapsilosis that required 80 μg/mL and in C. krusei between

Summary

Introduction

Candida spp. are commensal fungal species commonly colonizing human mucosal and skin surfaces, but they may become pathogenic in some particular scenarios such as treatment with antibiotics, immunocompromised patients, etc., producing in these cases infections that range from superficial to severe skin and mucosal lesions, to even systemic invasion at its worst degree [1]. Oral candidiasis is the most common opportunistic infection affecting the human oral cavity. It is caused by an overgrowth of Candida spp., being the most prevalent Candida albicans [2,3]. It is necessary to develop new treatments such as antimicrobial photodynamic therapy (aPDT). It is based on the use of photosensitizing molecules that are excited with visible light of the appropriate wavelength and reacts with the oxygen, generating reactive species of oxygen to destroy the target pathogen [5,6,7]

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Conclusion