Susceptibility of Candida albicans, Staphylococcus aureus, and Streptococcus mutans biofilms to photodynamic inactivation: an in vitro study

Abstract

The purpose of this study was to evaluate specific effects of photodynamic inactivation (PDI) using methylene blue as photosensitizer and low-power laser irradiation on the viability of single-, dual-, and three-species biofilms formed by C. albicans, S. aureus, and S. mutans. Biofilms were grown in acrylic discs immersed in sterile brain heart infusion broth (BHI) containing 5% sucrose, inoculated with microbial suspension (10(6) cells/ml) and incubated for 5 days. On the fifth day, the effects of the methylene blue (MB) photosensitizer at a concentration of 0.1 mg/ml for 5 min and InGaAlP laser (660 nm) for 98 s, alone and conjugated were evaluated. Next, the discs were placed in tubes with sterile physiological solution [0.9% sodium chloride (NaCl)] and sonicated for to disperse the biofilms. Ten-fold serial dilutions were carried and aliquots seeded in selective agar, which were then incubated for 48 h. Then the numbers CFU/ml (log(10)) were counted and analyzed statistically (ANOVA, Tukey test, p < 0.05). Scanning electron microscopy (SEM) on discs treated with PDI and control biofilms groups was performed. Significant decreases in the viability of all microorganisms were observed for biofilms exposed to PDI mediated by MB dye. Reductions (log(10)) of single-species biofilms were greater (2.32-3.29) than the association of biofilms (1.00-2.44). Scanning electron microscopy micrographs suggested that lethal photosensitization occurred predominantly in the outermost layers of the biofilms. The results showed that PDI mediated by MB dye, might be a useful approach for the control of oral biofilms.

Photoinactivation of Candida albicans using methylene blue as photosensitizer

“…Therefore, according to this study parameters and the cost-benefit ratio regarding the drug concentration and the clinical procedure time, the PDT protocol proved effective when used the 5-minutes incubation and the methylene blue concentration of 150 µg/mL. Using the 5-minutes incubation and methylene blue concentrations of 100μg/mL, 150μg/mL and 50 μg/ mL, Pereira et al 7 , Queiroga et al 9 and Giroldo et al 22 , respectively, observed a significant reduction in cell viability of Candida albicans species.…”

“…The studies of Dai et al 1 , Kato et al 4 , Teichert et al 6 , Pereira et al 7 , Souza et al 8 , Queiroga et al 9 , Munin et al 10 , Silva Martins et al 17 , Giroldo et al 22 and Souza et al 23 , investigated the effects of photodynamic therapy on the viability of Candida albicans using methylene blue as a photosensitizer. The results of these studies proved the antifungal effect of this treatment modality.…”

“…The studies that evaluated PDT effect on Candida albicans used different concentrations of methylene blue, from 10 µg/mL 22 to 500 µg/mL 6 and the most used incubation time was 5 minutes [7][8][9] . Therefore, to respond to the PDT effect hypothesis on the Candida albicans cells, this study used the concentration of 150 µg/ mL and the incubation time of 5 minutes.…”

“…For the performing the experiments, the Agar Sabouraud Dextrose-ASD (União Química, São Paulo, Brazil) culture medium was used with 5 μg/mL chloramphenicol, as preconized in Pereira et al 7 .…”

Susceptibility of clinical isolates of Candida to photodynamic effects of curcumin

“…Thus, it possible to suggest that CUR-mediated PDT can act against Candida biofilms in a similar way, simultaneously altering yeast metabolism and causing biofilm disarticulation. It has been suggested that lethal photosensitization is likely to occur in the outermost layers of C. albicans biofilms probably due to the superficial penetration of PS into the biofilm layers [43]. Since PDT can superficially disrupt the biofilm structure after a single application, it is possible to suppose that repeated cycles of the therapy may be capable of reducing the biofilm biomass, allowing deeper penetration of the PS and promoting higher levels of biofilm inactivation.…”