Photodynamic Antimicrobial Chemotherapy can kill planktonic cells of C. albicans

Photodynamic antimicrobial chemotherapy (PACT) consists in using a combination between a light source with a specific wavelength and a photosensitizing agent in order to cause bactericidal effects by reactive oxygen species production. Objective: The present study aimed to assess the effect of PACT on the viability of Candida albicans (ATCC 10231). Methods: Toluidine blue O (TBO, pre-irradiation time: 5 min) and red light emitting diode (LED, 630 nm, Biotable®, São Carlos, Brazil) were associated to produce photoinactivation outcomes on planktonic cells of C. albicans (0.5 McFarland). Samples were divided in four different experimental conditions, as follows: (i) untreated C. albicans suspensions; (ii) C. albicans suspensions incubated with 0.00025% or 0.0000025% TBO without irradiation; (iii) C. albicans suspensions irradiated with LED (120 J/cm2, 5 min) without sensitization by TBO; and (iv) C. albicans suspensions incubated with 0.00025% or 0.0000025% TBO and irradiated with LED. After treatment, C. albicans were plated onto Sabouraud agar plates and incubated in anaerobic conditions for 48 h at 37oC to determine the CFU counts. Results: Values are expressed in according to groups: (i) 1.0x10⁵ ± 1.6x10⁴; (ii) 5.0 x10⁴; ± 9.4x10³; (0,00025%), 7.9 x10⁴; ± 9.4x10³; (0,0000025%); (iii) 8.8 x10⁴; ± 3.5x10⁴; ; (iv) 5.3x10⁴; ± 1.4x10⁴; (0,00025%), 5.3x10⁴; ± 2.5x10⁴; (0,0000025%). Significant differences were observed among four groups (ANOVA, p<0.05). PACT significantly reduced CFU/mL, besides producing dose-dependent results. Conclusion: Planktonic cells of C. albicans can be killed after the use of PACT in vitro conditions. Presumably, this clinical approach might contribute with the control of fungal infections. Further in vitro and in situ studies must be performed to show the action of PACT on C. albicans biofilms.