Sterilization of Stainless-Steel Surfaces Using Ultraviolet Radiation Produced by Light-Emitting Diodes

Numerous studies have demonstrated that ultraviolet radiation in the C wavelength range produced by light-emitting diodes (UVC-LEDs) is effective for disinfection (<i>i.e.,</i> inactivation of vegetative bacteria and viruses). However, there are few efficacy data available to confirm its use as a sterilization technique (complete inactivation of bacterial spores). The present study evaluated the use of UVC-LED to achieve the sterilization of stainless-steel surfaces as a function of UVC dose and several other variables. Spores of <i>Bacillus atrophaeus</i> and two strains of <i>Bacillus pumilus</i> were used as indicator microorganisms. Results showed that the microorganism, spore loading, and inoculation method all affected whether complete inactivation was achieved. Under the tested conditions, sterilization of stainless-steel surfaces was achieved using UV-LED with doses that ranged from ∼4500 to 21,000 mJ/cm², and if spore deposition was low enough to prevent clumping and subsequent shielding. We found that spore deposition in which sterilization was achieved ranged from 2.9 to 6.2 log₁₀ colony-forming units/cm² and depended primarily on the microorganism/strain. Shielding of UV radiation diminished efficacy and may have also occurred from the presence of foreign material.