Harnessing the killing power of copper

‘We saw a greater than expected reduction’ in HAIs

The installation of copper objects and surfaces in patient rooms reduced infections by two major nosocomial pathogens by more than half, suggesting the antimicrobial metal could provide a powerful yet completely passive weapon for prevention.

“Placement of items with copper surfaces into ICU rooms as an additional measure to routine infection control practices could reduce the risk of [infections] as well as colonization with multidrug resistant microbes,” says study co-author Cassandra Salgado, MD, associate professor at the Medical University of South Carolina.1

The study focused on methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). However, the researchers say the results could be just as good with Clostridium difficile and multidrug-resistant Acinetobacter baumannii (MDR-Ab), pathogens that have a marked ability to persist on environmental surfaces in patient rooms.

The study was performed from July 12, 2010 to June 14, 2011 at three medical centers including the Medical University of South Carolina, the Memorial Sloan-Kettering Cancer Center, and the Ralph H. Johnson Veterans Affairs Medical Center. Patients who were admitted to the ICU of these hospitals were randomly assigned to receive care in a traditional patient room or in a room where items such as bed rails, tables, IV poles and nurse’s call buttons were made solely from copper-based metals. Both traditional patient rooms and rooms with copper surfaces at each institution were cleaned using the same practices.

The proportion of patients who developed health care associate infections (HAIs) or colonization with MRSA or VRE was significantly lower among patients in rooms with copper surfaces. Colonization rates were 7.1% for patients in copper rooms and 12.3% for those in standard rooms. The proportion of patients developing an HAI was significantly lower among those assigned to copper rooms (3.4%) compared with those in traditional rooms (8.1%).

“We had anticipated — and we had powered our study to detect — a 20% reduction because we thought that that would be clinically relevant. So we saw a greater than expected reduction,” Salgado says.

Though they do not replace the need for routine measures like hand hygiene and environmental cleaning, copper alloy surfaces offer a passive way to reduce bioburden, the authors noted.

Prime target: ‘Iraqibacter’

The study was funded through a contract from the U.S. Army Materiel Command and U.S. Department of Defense, agencies that are particularly interested in reducing infections by MDR-Ab. Dubbed “Iraqibacter,” MDR-Ab began its dramatic emergence in U.S. hospitals and nursing homes after initial cases were linked to soldiers returning from the Mideast wars. According to the Association for Professionals in Infection Control and Epidemiology, MDR-Ab can survive more than four months in a dry environment and is difficult to eradicate by surfaces when cleaning. “It is desiccation-tolerant and has often been recovered from the environment after routine discharge room cleaning.”2

Copper kills the pathogen in in vitro experiments, but there were not enough MDR-Ab cases in the study to measure any effectiveness in the clinical setting, says lead author Michael Schmidt, PhD, a professor of microbiology and immunology at the Medical University of South Carolina (MUSC) in Charleston.

“Copper works against every bacteria that has been tested,” he says. “It was one of our goals to assess the incidence of acinetobacter infections because it is a priority issue for the U.S. military. We are blessed in that our three study hospitals did not have an outbreak of acinetobactor, but it only takes a few ‘fugitives’ to sneak in to change your hospital demographics pretty quickly.”

The cost benefit of using copper is favorable if considered over time, he adds. The bed rail, for example, is negligible over the typical 10-year lifetime of a $50,000 hospital bed, Schmidt says.

“When you look at the amount of copper that we had on the bed rails it’s really a trivial amount of metal,” he says. “It is about 10 cents per patient over the life expectancy of the bed.”

On the basis of previous work to determine the microbial burden on frequently touched objects in the ICU, the researchers selected six items to fabricate from copper alloys. Four items were identical at all hospitals: bed rails, “over” bed tables, intravenous poles, and arms of the visitor’s chair. The other two items varied slightly, but included a nurses’ call button, a computer mouse and the bezel of the touchscreen monitor. Objects were fabricated by the same manufacturers for each site from a variety of solid copper alloys selected on the basis of ease of fabrication for each component, durability, ability to withstand cleaning, and aesthetics. Each alloy was registered with the Environmental Protection Agency for its antimicrobial ability.

Though all facilities followed preexisting comparable cleaning protocols with hospital-grade disinfectants, the researchers were wary that the presence of copper would change cleaning behavior.

“The copper is definitely a visual trigger so [we looked for a possible] Hawthorne effect,” Schmidt says. “Were the health care workers behaving differently — were they cleaning differently? The answer was no. The environmental services team paid no attention to whether it was copper or plastic, they just came in and did their business and moved on.”

An additional “internal control” not revealed to study participants was done through culture sampling of a non-copper bed footboard in each room. “The results did not appreciably differ from bed to bed regardless of whether or not there was copper in the room, so again there was no behavioral difference,” Schmidt says.

Though the results are promising, the study has several limitations, Salgado adds.

“This was a study of ICU patients so it’s not clear to us if the copper surfaces will be effective outside the ICU in different patient populations,” she says. “That will be important to study. It’s also not entirely clear how many copper surfaces are needed in the environment to repress the microbial burden and mitigate the risk of HAIs.”

Further study will also take a closer look at individual patients to determine which copper object or surface has the most protective effect, she says.

Reference

1. Salgado CD, Sepkowitz K, John J, et al. Copper Surfaces Reduce the Rate of Healthcare-Acquired Infections in the Intensive Care Unit. Infect Control Hosp Epi 2013;34:5.

2. Association for Professionals in Infection Control and Epidemiology: Guide to the Elimination of Multidrug-resistant Acinetobacter baumannii Transmission in Healthcare Settings. 2010: ow.ly/lfftO