Editorial commentary: climbing the evidentiary hierarchy for environmental infection control.

Increasing concern over multidrug-resistant organisms (MDROs), especially vancomycin-resistant enterococci (VRE), Clostridium difficile, and multidrugresistant gram-negative bacteria (MDRGNB), has led to increasing attention being paid to the role of high-touch environmental surfaces in transmission. Our current understanding of the roles of environmental surfaces in MDRO transmission include the following: (1) a primary role with transmission from source patient to environmental surface to subsequent patient, and (2) a secondary role from source patient to environmental surface to hands of healthcare personnel to subsequent patient. Either a prior room occupant or a contemporaneous patient sharing reusable medical equipment is the source patient in most primary transmission events. Standard environmental cleaning and disinfection entails manual cleaning and application of a disinfectant, often utilizing a detergent disinfectant. In addition to new disinfectants with greater potency and shorter contact times, new technological advances include “nontouch disinfection” (NTD) methods, the most developed of which are hydrogen peroxide vapor (HPV), and automated germicidal ultraviolet irradiation. Both methods appear highly efficacious in inactivating the microbial bioburden present on surfaces, and both remove much of the variance inherent in human cleaning activity via a high degree of automation and feedback loops for verification that contact or irradiation times are adequate [1–3]. Despite these advances, demonstrating the clinical impact of both old and new environmental cleaning and disinfection technologies remains challenging. We propose an evidentiary hierarchy for assessing any environmental disinfection strategy (Figure 1), beginning with a foundation (ie, level I) of laboratory efficacy studies similar to those required for registration by the Environmental Protection Agency [4]. Numerous patient and practice factors confound the relationship between environmental bioburden reductions and MDRO transmission interruption, from the number of patients on antibiotics with wounds, devices, and diarrhea (rendering them either more contagious or susceptible to colonization), to rates of compliance with hand hygiene and isolation, to interventions aimed at source control such as chlorhexidine bathing. Because only a small proportion of all MDRO acquisitions lead to eventual infection, linking infection reductions to environmental bioburden reductions (ie, level V of Figure 1) is even more challenging. However, because infections correlate more closely than colonization with mortality, excess length of stay, and cost, such linkage will eventually become necessary to calculate the cost-effectiveness of new technologies. Such a hierarchy can assist the development of a new disinfection technology, guiding industry in demonstrating achievement at a lower level in the hierarchy before investment is made at a higher level. It also highlights the need for tools to link achievements at lower levels (eg, achievable log10 reductions in the laboratory or as part of an in-use study) to the likelihood of success at a higher level. Standardized methods for environmental and hand sampling, microbiologic cultures, and assessment of adherence to standard environmental cleaning, hand hygiene, and isolation precautions will all be important to make the climbing of this hierarchy more efficient. The report by Passaretti et al in this issue of Clinical Infectious Diseases, in which investigators found that HPV decontamination of MDRO patient rooms was associated with a 45% reduction in environmental contamination and 80% reduction in acquisition of VRE among patients with a prior MDRO-colonized Received 11 September 2012; accepted 18 September 2012; electronically published 5 October 2012. Correspondence: L. Clifford McDonald, MD, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Rd, MS07, Atlanta, GA 30333 ([email protected]). Clinical Infectious Diseases 2013;56(1):36–9 Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved 2012. DOI: 10.1093/cid/cis845