Description and results of a new method for assessing real-life performance of a UV-C disinfection robot

Background: Due to the disadvantages of manual disinfection of patient rooms, mobile disinfection robots using ultraviolet C (UV-C) radiation are increasingly being used. Assessing their in situ effectiveness remains challenging. Aim: This study describes a new method to prove adequate in situ disinfection (>= 5-log reduction in bacterial load), and uses this method to assess the efficacy of a mobile disinfection robot using UV-C radiation. Methods: Agar plates serving as proxies for smooth surfaces in patient rooms were inoculated with bacterial suspension and placed on various surfaces in a patient room. After irradiation by an automated mobile UV-C robot, reduction in colony growth was determined by comparing the irradiated plates to a reference series of non-irradiated plates, enabling the evaluation of whether an adequate reduction in colony-forming units (CFU's) of >= 5-log was reached on these irradiated surfaces. Findings: The new technique described here proved a successful method for demonstrating an in situ >= 5-log reduction in CFU's for five different bacterial pathogens. Of the 32 plates placed on UV-accessible surfaces, 31 showed an adequate reduction in CFU's of >= 5-log. One plate could not be assessed. Conclusion: Inoculated agar plates placed in patient rooms before irradiation and subsequently compared to a reference series can be used to assess in situ efficacy of mobile disinfection robots using UV-C radiation. Our findings support the idea that UV-C robots, used adjunctively to conventional manual washing and disinfection, may achieve adequate bacterial load reduction on UV-accessible smooth surfaces in patient rooms for a selected subset of pathogens. (c) 2023 The Authors. Published by Elsevier Ltd on behalf of The Healthcare Infection Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).