BOSTON – Although copper is not officially considered a precious metal, its antimicrobial properties suggest it may be priceless in the fight against the growing threat of hospital-acquired infections, according to new data presented at the annual meeting of the Infectious Diseases Society of America.
Previously shown to reduce the environmental bioburden when placed into medical intensive care unit (MICU) patient rooms, copper surfaces significantly reduced the acquisition rate of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus relative to standard-material surfaces in a randomized controlled trial. The study compared the effect of both types of surfaces on the rates of hospital-acquired infections (HAI) in 564 medical intensive care unit patients, reported Dr. Cassandra Salgado of the Medical University of South Carolina in Charleston.
"Environmental surfaces harbor micro-organisms. In an earlier study, we reported that copper surfaces, including bedrails, intravenous poles, overbed tables, chairs, computer monitor bezel, and call button or computer mouse, reduced the median environmental bioburden by more than 97% compared with noncopper surfaces, such as plastic, wood, stainless steel, and chrome, in MICU patient rooms," Dr. Salgado noted. "In this study, our goal was to document the effect of copper surfaces on the rate of health care–acquired infections specifically."
Toward this end, the investigators randomly placed 564 patients admitted to the MICU of three hospitals between July 12, 2010, and May 13, 2011, into rooms with either standard or copper surfaces and followed them prospectively for the development of HAIs, defined by the National Healthcare Safety Network (NHSN), or for new MRSA or VRE colonizations. The clinical characteristics of patients in both groups were similar with respect to age, gender, race, APACHE II score, presence of infection on admission, or MICU length of stay, Dr. Salgado noted. Standard hand washing and environmental cleaning protocols were monitored and maintained throughout the study and there were no differences between the uses of these practices in either setting, she said.
Over the course of the study, 47 patients (8.3%) developed an HAI, including 29 (5.1%) identified as MRSA or VRE, Dr. Salgado reported. The overall incidence of HAI per 1,000 patient days was 12.23, with significantly lower rates observed in copper vs. standard rooms, at 8.95 vs. 15.16 per 1,000 patient days, respectively, she said. In addition, the overall rate of MRSA or VRE acquisition was 7.55 per 1,000 patient days and was significantly lower in copper vs. standard rooms, at 6.12 vs. 8.8 per 1,000 patient days.
In a subpopulation of patients admitted to rooms where all 6 copper-surface objects remained in the room during the entire MICU stay, "there was an even greater effect on reduction of [HAIs] compared with those never exposed to the copper surfaces," Dr. Salgado said. Specifically, the HAI acquisition rate per 1,000 patient days was 6.88 among patients in the full-time copper surface rooms compared with 15.72 among those not exposed to the copper surfaces.
The antimicrobial action of copper is attributed to the release of ions that penetrate the cell walls of microbes and disrupt their ability to function and reproduce, Dr. Salgado explained. Importantly, she added, the effect is continuous, even when combined with other metals.
Considering the contribution of environmental bioburden on the risk of hospital-acquired infections in the MICU as demonstrated by this investigation, efforts to reduce the bioburden, including the replacement of standard surface objects with copper surface alternatives, are warranted, Dr. Salgado stated.
This study was supported by a research grant from the U.S. Department of Defense. Dr. Salgado disclosed no additional conflicts of interest.