Photodynamic inactivation of Candida albicans mediated by a low density of light energy

Abstract

Shorter times and lower energies of application of light sources are desirable to use photodynamic antimicrobial chemotherapy (PACT) to the clinical control of candidiasis, especially among babies and children. Light energies ranging from 39.5 to 100 J/cm(2) were previously applied to kill Candida albicans by PACT. The present study evaluated the efficacy of a combination of 0.05 mg/mL toluidine blue O (TBO) and a short time of application (60 s) and a low density of light energy (18 J/cm(2)) of a red light-emitting diode (LED) in killing C. albicans planktonic cells. Standard suspensions of C. albicans were randomly assigned for four treatment groups: control (L-P-), LED alone (L+P-), TBO alone (L-P+), and PACT (L+P+). After treatments, serial dilutions of suspensions were prepared and streaked on Sabouraud dextrose agar to determine colony-forming units of C. albicans per milliliter (CFU/mL). The results were analyzed by ANOVA and Tukey's post-hoc test (P < 0.05). PACT significantly reduced CFUs of C. albicans in comparison to other three treatments. Our results demonstrated a fungicidal effect of PACT mediated by a shorter time of application of LED on C. albicans planktonic cells. Further in vivo studies are needed to elucidate the efficacy of PACT to treat human fungal infections.

Influence of Incubation Time on Ortho-Toluidine Blue Mediated Antimicrobial Photodynamic Therapy Directed against Selected Candida Strains—An In Vitro Study

“…Other incubation times used in that study were 1 min [46,47], 10 min [48] and 20 min [29]. In two other studies of TBO-mediated aPDT, the applied PIT was not reported [49,50]. All these studies showed the efficacy of the therapy as a reduction in the number of cells or % CFU/mL, but only that by Nielsen et al showed complete elimination of C. albicans from the planktonic solution (LED 635 nm, 37.7 J/cm 2 , 400 mW, TBO concentration 0.226 mM, PIT 1 min) [47] and the others showed only a partial reduction.…”

Growth models of fractal interfaces in the description of microorganism colony growth: effect of photodynamic inactivation

“…This equation was also satisfied in analysis of the growth of the fungus Aspergillus nidulans [29]. The growth of C. albicans may have been inhibited by the photoinactivation phenomenon [30], altering the exponents of scale. Therefore, the variation in the growth rate must be considered as a factor of modification in the pattern of microorganism development.…”

Combined 624-nm and 850-nm illumination at low rates leads to enhanced inhibition of Candida albicans

“…18,19 Barbario et al recently demonstrated a significant kill rate of C. albicans when exposed to a combination of 0.05 mg/mL toluidine blue O and 18 J/cm 2 of red light. 20 In an in vivo study, Dai et al found UVC light (254 nm) to be superior to a topical antifungal drug in treating C. albicans. 5 Based on these results, it can be said that C. albicans can be treated with various wavelengths when appropriate photosensitizers are included.…”