Antimicrobial efficacy of an experimental UV-C robot in controlled conditions and in a real hospital scenario

Background

Among no-touch automated disinfection devices, ultraviolet-C (UV-C) radiation has been proven to be one of the most effective against a broad spectrum of micro-organisms causing healthcare-associated infections.

Aim

To evaluate the antimicrobial efficacy of an experimental UV-C robotic platform, under controlled conditions and in a real hospital scenario, when used to implement the standard cleaning operating protocol (SOP).

Methods

In vitro, following dose calibration tests, bactericidal and virucidal efficacy were tested in accordance with American Society for Testing and Materials International Standard E3135-18. In hospital settings, 12 high-touch surfaces were sampled after healthcare activity (dirty condition), after SOP alone, and after SOP + UV-C treatment, with a total of 180 samples.

Findings

In vitro, <4 mJ/cm² was required to remove Staphylococcus aureus and Pseudomonas aeruginosa completely, 194 mJ/cm² was required to inactivate adenovirus HadV5 completely, and 38.8 mJ/cm² was sufficient to inactivate coronavirus 229E completely. In the real hospital scenario, the mean UV-C dose emitted on the sampled surfaces was 29.31 mJ/cm². A significant difference was found after SOP alone (P=0.022) and after SOP + UV-C treatment (P=0.007) compared with the dirty condition. The average percentage reduction in the total viable count (TVC) was 67% after SOP alone and 96% after SOP + UV-C treatment.

Conclusions

Comparison of the tests conducted in vitro and in the real hospital scenario showed that the efficacy of the UV-C robot was reduced in the hospital setting, as a higher dose was needed to obtain a reduction in the TVC.