Numerous studies have demonstrated that ultraviolet radiation in the C wavelength range produced by light-emitting diodes (UVC-LEDs) is effective for disinfection (i.e., 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 Bacillus atrophaeus and two strains of Bacillus pumilus 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.
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