Blue LED Light Attenuates the Bacterial Bioburden in Chronic Wounds Transiently but Dose-Dependently

Phototherapy may improve chronic wound healing through different mechanisms. We have investigated whether escalating doses of blue LED light treatment (λ = 405 nm) impact the chronic wound microbiota. Twenty-two patients with chronic wounds were sequentially assigned to a low dose (20 J/cm², n = 7), medium dose (60 J/cm², n = 8), or high dose (100 J/cm², n = 7) of blue LED light. Bacterial counts, cytokine levels in wound fluid obtained by surface swab and wound size were determined at baseline. Four days after the baseline visit, wounds were irradiated six times with blue LED light at 2-3-day intervals over 2 weeks. Bacteria were semi-quantified just before and directly after each irradiation. Blue LED light reduced bacterial counts dose-dependently (p < 0.0001) and the mean ± SD log₁₀ reduction of colony-forming units/swab from the six treatments was significantly larger for 60 J/cm² (1.55 ± 0.33) and 100 J/cm² (1.82 ± 0.22) compared with the 20 J/cm² fluence (0.65 ± 0.095). The reductions of the 60 J/cm² and 100 J/cm² fluences did not differ (p = 0.180). Bacterial counts at follow-up (p = 0.668), 4 days after the last irradiation and the levels of selected cytokines (IL-1α, IL-1β, IL-6, GM-CSF, TNF-α and VEGF) did not change significantly from baseline. The linear healing rates from baseline to follow-up did not differ (p = 0.815) among the three groups. In conclusion, blue LED light treatment resulted in an immediate but transient reduction of bacterial quantities in chronic wounds, with no apparent advantage to increasing the dose from 60 J/cm². There was no significant effect on wound healing of blue light treatment.