In vitro effectiveness of 455-nm blue LED to reduce the load of Staphylococcus aureus and Candida albicans biofilms in compact bone tissue

The aim of this study was to evaluate the effectiveness of a 455-nm blue light-emitting diode (LED), at different application times, to reduce the load of Staphylococcus aureus and Candida albicans biofilms applied to compact bone tissue. The microorganisms S. aureus (ATCC 25923) and C. albicans (ATCC 18804) were used to form biofilms on 160 specimens of compact bones that had been divided into eight experimental groups (n = 10) for each microorganism, according to the times of application of the 455-nm blue LED (1, 2, 3, 4, 5, 7, and 10 min) with an irradiance of 75 mW/cm². After LED application, decimal dilutions of microorganisms were performed, plated on BHI or Sabouraud agar and incubated for 24 h/35 °C to obtain CFU/mL counts. The findings were statistically analyzed using a ANOVA 5 %. For the group of S. aureus biofilms, all groups of 455-nm LED application differ compared with the control group (p < 0.05), in which no treatment was given. The largest reduction was obtained in the group receiving LED for 10 min (p = 0.00); within this group, a 3.2 log reduction was observed. For the C. albicans biofilms, only those samples receiving 3, 7, and 10 min of LED application presented a significant difference compared with the control group (p < 0.00), indicating that longer application times are required to achieve efficacy. The results of this study show that 455-nm LED light was effective to reduce the load of S. aureus and C. albicans biofilms, especially during 10 min of application.