• S Ali, S Yui, M Muzslay, and WilsonA P RAPRDepartment of Microbiology, University College London Hospitals, London, UK. Electronic address: peter.wilson@uclh.org..
• Environmental Microbiology Research Laboratory, University College London Hospitals, London, UK.
• J. Hosp. Infect. 2017 Oct 1; 97 (2): 180-184.

BackgroundUltraviolet (UV) light decontamination systems are being used increasingly to supplement terminal disinfection of patient rooms. However, efficacy may not be consistent in the presence of soil, especially against Clostridium difficile spores.AimTo demonstrate in-use efficacy of two whole-room UV decontamination systems against three hospital pathogens with and without soil.MethodsFor each system, six patient rooms were decontaminated with UV irradiation (enhanced disinfection) following manual terminal cleaning. Total aerobic colony counts of surface contamination were determined by spot-sampling 15 environmental sites before and after terminal disinfection and after UV irradiation. Efficacy against biological indicator coupons (stainless-steel discs) was performed for each system using test bacteria (106 cfu EMRSA-15 variant A, carbapenemase-producing Klebsiella pneumoniae) or spores (105 cfu C. difficile 027), incorporating low soiling [0.03% bovine serum albumin (BSA)], heavy soiling (10% BSA) or synthetic faeces (C. difficile only) placed at five locations in the room.FindingsUV disinfection eliminated contamination after terminal cleaning in 8/14 (57%) and 11/14 (79%) sites. Both systems demonstrated 4-5 log10 reductions in meticillin-resistant Staphylococcus aureus and K. pneumoniae at low soiling. Lower and more variable log10 reductions were achieved when heavy soiling was present. Between 0.1 and 4.8 log10 reductions in C. difficile spores were achieved with low but not heavy soil challenge.ConclusionTerminal disinfection should be performed on all surfaces prior to UV decontamination. In-house validation studies should be considered to ensure optimal positioning in each room layout and sufficient cycle duration to eliminate target pathogens.Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

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