Self-Disinfecting Surfaces

Abstract

Affiliations: 1. Department of Medicine, University of North Carolina Medical School, Chapel Hill, North Carolina; 2. Department of Hospital Epidemiology, University of North Carolina Health Care, Chapel Hill, North Carolina. Received October 30, 2011; accepted October 31, 2011; electronically published December 7, 2011. 2011 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2012/3301-0003$15.00. DOI: 10.1086/663648 Contamination of environmental surfaces in hospital rooms is now recognized as playing an important role in the transmission of several key healthcare-associated pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), Clostridium difficile, Acinetobacter species, and norovirus. All of these pathogens have been demonstrated to persist in the environment for hours to days (and in some cases for months), to frequently contaminate the environmental surfaces in the rooms of colonized or infected patients, to transiently colonize the hands of healthcare personnel (HCP), to be transmitted to patients by HCP, and to cause outbreaks in which environmental transmission was deemed to play a role. Furthermore, hospitalization in a room in which the previous patient had been colonized or infected with MRSA, VRE, C. difficile, or Acinetobacter species has been shown to be a risk factor for colonization or infection with the same pathogen in the newly admitted patient. Pathogen transfer from an affected patient to a susceptible host occurs most commonly via the hands of HCP, but contaminated surfaces, objects, and air can be directly or indirectly involved in the transmission pathway. These transmission pathways and methods to interrupt transmission have been diagramed. Transmission can be greatly reduced by hand hygiene of HCP before and after each patient contact and by appropriate disinfection of shared medical devices between patients. However, reducing or eliminating surface contamination is crucial to preventing acquisition of healthcare pathogens by patients who are newly admitted to rooms previously occupied by colonized or infected patients and to minimizing the risk of contaminating the hands of HCP. Potential methods of decreasing contamination of environmental surfaces in hospital rooms have included routine and terminal room disinfection with chemical germicides and, more recently, the use of “no-touch” methods of terminal room decontamination with UV light or aerosolized and/or vaporized hydrogen peroxide. Unfortunately, there are major limitations associated with currently available methods of room decontamination. Multiple studies have demonstrated that less than 50% of hospital room surfaces are adequately cleaned and disinfected when chemical germicides are used, although with implementation of enhanced performance feedback, education, and other interventions, the frequency of appropriate cleaning can be increased to 71%–77%. The major limitation of UV light and hydrogen peroxide is that, because this method requires the removal of patients and HCP from the room, it can be used only for terminal disinfection. Other limitations include the high acquisition costs of room decontamination units and increasing the time of room turnover. In the past several years, another method of reducing contamination of room surfaces has emerged: self-disinfecting surfaces (Table 1). Such surfaces have also been called “selfsanitizing,” and because microbial killing requires direct contact with the surface, the term “contact killing” has also been used. One novel method to achieve contact killing is to cover room surfaces with a transition metal, such as copper or silver. Such metals influence microorganisms by affecting their growth, morphology, and biochemical activities. Toxicity is a result of the blocking of functional groups of important molecules (eg, enzymes), displacement or substitution of essential ions from cellular sites, denaturation and inactivation of enzymes, generation of reactive hydroxyl radicals, and disruption of cellular membrane integrity. Copper is an essential trace element in most living organisms and has been used for centuries as a medicinal as well as to prevent growth of barnacles and weeds on the hulls of ships. Copper surfaces have been demonstrated to be cidal to important healthcare-associated pathogens, including MRSA, Acinetobacter species, Pseudomonas aerugonosa, and influenza virus. Experimental inoculation of copper surfaces has demonstrated that dry metallic surfaces were more antimicrobial than were moist surfaces. On dry surfaces, vegetative bacteria were killed within a few minutes. How soiling,