Superiority of manual disinfection using pre-soaked wipes over automatic UV-C radiation without prior cleaning

Abstract

The efficacy of ultraviolet C (UV-C) radiation against a broad spectrum of microorganisms has been demonstrated in several studies, but differences in the specific doses and the extent of microbial reduction were found. Furthermore, the conditions of laboratory tests differ greatly from reality, so that efficacy achieved here may not necessarily be assumed in reality. Consequently, it is important to investigate the effectiveness of UV-C in representative field trials. The aim was therefore to develop and establish a field test to evaluate automatic UV-C in comparison to manual disinfection. Before and after disinfection, samples were repeatedly collected from naturally highly contaminated surfaces using swab technique to obtain representative data sets for disinfected and non-disinfected surfaces. Subsequently, the log reduction values (LRV) and the disinfection success were evaluated for UV-C radiation and full compliant manual disinfection using alcohol based wipes. Surfaces that are naturally contaminated with bacteria on a regular and nearly uniform basis have been identified as particularly suitable for field testing. Mean contamination was reduced from 23.3 to 1.98 cfu/cm2 (LRV 0.9) and 29.7 to 0.26 cfu/cm2 (LRV 1.2) for UV-C and manual disinfection, respectively. UV-C disinfection achieved 75.5% successful disinfected surfaces, whereas manual disinfection showed 98.1%. Full compliant manual disinfection showed slightly greater LRV and disinfection success than automatic UV-C disinfection. Successful, operator-independent UV-C disinfection still has the potential to improve disinfection performance in addition to manual disinfection.