500 - Novel Use of a Targeted Ultraviolet Light Device for the Decontamination of a Single-Use Filtering Facepiece Respirator

Background: The use of disposable or single-use filtering facepiece respirators (FFRs), like N95s, are an important component of personal protective equipment for healthcare personnel in treating patients with a respiratory virus and not approved for reuse.  The current pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in the limited availability of respirators.  As a result, the decontamination of FFRs is a potential solution for reuse in order to conserve supplies.  However, the efficacy of disinfection for a contaminated FFR needs to be evaluated.  This experiment examined the effectiveness of a targeted ultraviolet C (UVC) device for the decontamination of a single-use respirator.

Methods: To mimic an aerosolized droplet contaminating a cellulose based respirator, a 6 mm cotton disk was inoculated with a 10 μL aliquot of Bacillus subtilis endospores.  The disks were placed directly under the UVC light with 6 inches between the bulb and disk.  The samples were then exposed for 90 seconds, 3 minutes, 5 minutes, and 10 minutes, respectively.  After specified exposure time, the disks were turned over, and the other side was exposed for the same time interval as the previous side.  Disks were placed in a 10 mL nutrient broth and incubated at 30°C for 48 hours.  Lastly, the serially diluted specimens were plated onto nutrient agar, incubated for 48 hours, and the log₁₀ colony forming units (CFU) reductions were enumerated by comparing disks after decontamination versus untreated controls.

Results: The log₁₀ CFU reduction of B. subtilis spores over all time intervals were significant when compared to controls.  The mean reduction of spores on the cotton disks were 2.5 log after 90 seconds, 4 log after 3 minutes, and >6 log for both 5 and 10 minutes with no measurable recovery of spores for the last two exposures.

Conclusion: The use of targeted UVC was very successful in reducing the B. subtilis spores from a cotton disk within 90 seconds, and the 100% elimination of the spores after 5 minutes. Even though a pandemic virus was not used, the sporicidal efficacy suggests this device could be effective at inactivating SARS-CoV-2.  Based upon these findings, a targeted UVC device could be utilized for the decontamination of a single-use respirator needed during times of shortages.