Use of UV-C radiation to disinfect non-critical patient care items: a laboratory assessment of the Nanoclave Cabinet
1 Clinical Microbiology and Virology, University College London Hospitals NHS Foundation Trust, London, UK
2 Great Ormond Street Hospital for Sick Children, London, UK
3 Hospital Infection Research Laboratory, Queen Elizabeth Hospital, Birmingham, UK
4 Department of Microbiology, UCLH Environmental Research Group, Royal Free Hampstead NHS Trust, London, NW3 2QG, UK
BMC Infectious Diseases 2012, 12:174 doi:10.1186/1471-2334-12-174Published: 3 August 2012
The near-patient environment is often heavily contaminated, yet the decontamination of near-patient surfaces and equipment is often poor. The Nanoclave Cabinet produces large amounts of ultraviolet-C (UV-C) radiation (53 W/m2) and is designed to rapidly disinfect individual items of clinical equipment. Controlled laboratory studies were conducted to assess its ability to eradicate a range of potential pathogens including Clostridium difficile spores and Adenovirus from different types of surface.
Each test surface was inoculated with known levels of vegetative bacteria (106 cfu/cm2), C. difficile spores (102-106 cfu/cm2) or Adenovirus (109 viral genomes), placed in the Nanoclave Cabinet and exposed for up to 6 minutes to the UV-C light source. Survival of bacterial contaminants was determined via conventional cultivation techniques. Degradation of viral DNA was determined via PCR. Results were compared to the number of colonies or level of DNA recovered from non-exposed control surfaces. Experiments were repeated to incorporate organic soils and to compare the efficacy of the Nanoclave Cabinet to that of antimicrobial wipes.
After exposing 8 common non-critical patient care items to two 30-second UV-C irradiation cycles, bacterial numbers on 40 of 51 target sites were consistently reduced to below detectable levels (≥ 4.7 log10 reduction). Bacterial load was reduced but still persisted on other sites. Objects that proved difficult to disinfect using the Nanoclave Cabinet (e.g. blood pressure cuff) were also difficult to disinfect using antimicrobial wipes. The efficacy of the Nanoclave Cabinet was not affected by the presence of organic soils. Clostridium difficile spores were more resistant to UV-C irradiation than vegetative bacteria. However, two 60-second irradiation cycles were sufficient to reduce the number of surface-associated spores from 103 cfu/cm2 to below detectable levels. A 3 log10 reduction in detectable Adenovirus DNA was achieved within 3 minutes; after 6 minutes, viral DNA was undetectable.
The results of this study suggest that the Nanoclave Cabinet can provide rapid and effective disinfection of some patient-related equipment. However, laboratory studies do not necessarily replicate ‘in-use’ conditions and further tests are required to assess the usability, acceptability and relative performance of the Nanoclave Cabinet when used in situ.