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.