Daily Phototherapy with Red Light Reduces Candida albicans Biofilm Biomass

Objectives: Candida albicans is the most common species associated with oral manifestations, such as oropharyngeal candidiasis. Infections caused by Candida are frequently associated to biofilm formation. Biofilm is a microstructure of cells adhered to a surface and incorporated into an extracellular matrix that works as a scaffold and limits the diffusion of substances. In some biofilms, the microorganisms can account for less than 10% of the biomass, while the matrix can account for over 90%. Considering the high rate of resistant pathogens to conventional antifungal treatments, studies have considered new approaches to control biofilm development. This study aimed to compare the effects of daily phototherapy using red light (570-690 nm) for 1 min on biofilms of a wild-type (WT, SN425) and two Candida albicans mutant strains with deficiency on biofilm formation (Δ/Δ tec1 and Δ/Δ efg1).
Methods: Biofilms were exposed twice-daily to red light (RL – 87.6 J/cm²) during their 48 h development. Biofilms were analyzed for colony-forming units (CFU) and total biomass (mg). Positive control (PC) biofilms were treated with 0.12% chlorhexidine (CHX) and non-treated biofilms were the negative control (NC). Data was analyzed by one-way ANOVA with Tukey post-hoc test (α=0.05).
Results: RL did not reduce CFU of any of the strains when compared to PC (p>0.05). However, biofilms of the WT strain had their biomasses significantly reduced by RL when compared to the NC (p=0.027). Biofilms from the mutant Δ/Δ efg1 had their biomasses significantly reduced by CHX (p=0.033) and RL (p=0.011) when compared to NC. Similarly, biofilms of the mutant Δ/Δ tec1 had their biomasses significantly reduced by CHX (p=0.002) and RL (p=0.020) when compared to NC.
Conclusions: In conclusion, RL is a promising approach to reduce the biomasses of C. albicans biofilms by potentially acting on the biofilm matrix.