Inactivation of Bacillus anthracis and Bacillus atrophaeus spores on different surfaces with ultraviolet light produced with a low-pressure mercury vapor lamp or light emitting diodes

Aims To obtain quantitative efficacy data of two ultraviolet light (UVC) technologies for surface inactivation ofBacillus anthracisAmes andBacillus atrophaeusspores. Methods and Results Spores were deposited onto test coupons and controls of four different materials, via liquid suspension or aerosol deposition. The test coupons were then exposed to UVC light from either a low-pressure mercury vapor lamp or a system comprised of light emitting diodes, with a range of dosages. Positive controls were held at ambient conditions and not exposed to UVC light. Following exposure to UVC, spores were recovered from the coupons and efficacy was quantified in terms of log(10)reduction (LR) in the number of viable spores compared to that from positive controls. Conclusions Decontamination efficacy varied by material and UVC dosage (efficacy up to 5 center dot 7 LR was demonstrated). There was no statistical difference in efficacy between the two species or between inoculation methods. Efficacy improved for the LED lamp at lower relative humidity, but this effect was not observed with the mercury vapor lamp. Significance and Impact of the Study This study will be useful in determining whether UVC could be used for the inactivation ofB. anthracisspores on different surface types.