Copper and its alloys may be the latest weapon against superbugs.
Jean M. Hoffman Senior Editor
The natural antimicrobial and self-decontaminating properties of copper make it a candidate for use in hospitals and other health-care facilities on touch surfaces that are potential reservoirs of infection. Lab tests by researchers in the U.K. and U.S. have established that copper and its alloys (bronze, brass, copper-nickels, and nickel-silvers) can quickly and efficiently eradicate several different pathogens Escherichia coli O157:H7 (E. coli), Influenza A, and Methicillin- resistant Staphylococcus aureus (MRSA) which are the source of many hospital-acquired infections.
The findings are being put to the test at Selly Oak Hospital in Birmingham, England, Memorial Sloan-Kettering Cancer Center in New York City, the Medical University of South Carolina, and the Ralph H. Johnson VA Medical Center, both in Charleston, S.C. The 18-month clinical trial at Selly Oak, as well as those being conducted in the U.S., will pit copper door handles and push plates, IV poles, bathroom taps, toilet flush-handles, grab rails, and other frequently touched surfaces against traditional metal fittings in a battle against certain superbugs and other bacteria.
Research by Bill Keevil and his team at University of Southhampton in the U.K. examined survival rates of various bacteria dried on the surfaces of 25 copper (Cu) alloys and other materials including polyethylene (PE), 304 stainless steel (UNS S30400, a variation of the 18% chromium 8% nickel austenitic alloy, the most familiar and most frequently used alloy in the stainless-steel family), and a antimicrobial silver-ion (Ag+)-coated 304 stainless steel.
E. coli, a food-born pathogen, that in the elderly and children can lead to life-threatening hemolytic uremia syndrome, was one of the first bacteria tested. Room-temperature results showed that on pure and 99%-copper substrates extremely high levels of the bacteria dropped two orders of magnitude in only 45 min and were completely gone in 75 min. There was a similar pattern at 4°C (39°F). It took between 75 and 180 min for a drop in bacterial counts from 100 million to total eradication.
The inhibition effects of the brasses (Cu-zinc) and bronzes (copper and another alloying ingredient, generally tin) is similar, but generally less than that seen in the coppers, at times taking upwards of 2 hr or more for bacteria counts to drop to zero.
However, the results for the remaining three substrates (PE, 304 stainless steel, and Ag+-coated 304 stainless steel) were bleak. The PE saw no significant drop in bacteria counts, while the 304 stainless steel, widely used for food-processing equipment, had little or no inhibition effect. High levels of bacteria remained on the 304 alloy after 4 hr and were not much lower than that found on the PE.
During the first two days of a 28-day exposure, the stainless steel saw a five-log drop in bacteria count to about 1,000. Similarly, the antimicrobial Ag+-coated stainless steel showed a four-log drop in bacteria count to 10,000 in two days. But this is still high, especially when ingestion of only 10 to 50 individual bacteria may be enough to cause infection. According to the National Audit Office in the U.K., 300,000 patients pick up infections in hospitals annually. At least 5,000 are likely to die as a result. Likewise, the U.S. Centers for Disease Control and Prevention (CDC) estimates that U.S. hospitals account for an estimated 2 million infections and 90,000 deaths annually.
MRSA in the crosshairs
The Keevil team also took aim at one of the more virulent strains of MRSA. MRSA infections are usually asymptomatic in healthy individuals, but can become problematic if they enter the bloodstream. To individuals with weakened immune systems, these infections can be deadly. The nostrils, respiratory tract, open wounds, intravenous catheters, and urinary tract are potential infection sites.
Test results show that copper, and to a lesser extent brass, completely react with the MRSA. The alloys are believed to inhibit respiration and in effect suffocate the pathogen in as little as 1.5 hr for copper and 4.5 hr for brass, says Keevil.
But tests show that it is not just MRSA that can be killed by copper. “A newer threat,” says Keevil, “is the superbug clostridium difficile. Dubbed C. diff. by medical personnel. An infection with this virulent pathogen can range in severity from asymptomatic to life threatening. People are most often infected in hospitals, nursing homes, or institutions.”
Scientists are already considering wider medical applications for copper, says Keevil, including a possible defense against bird flu. Experiments by the Southhampton team have shown that copper can kill the human flu virus. “Avian flu is almost identical to normal human flu,” says Keevil. “Although we haven’t done the work yet, we would predict the same results.”
Copper Clinical Trial
Selly Oak was chosen for the copper clinical trial, because it is a multispecialist center with an advanced microbiology lab. Because 80% of MRSA transmission is through surface contact, copper replaced stainless-steel door handles and push plates in one ward, along with bathroom taps, toilet flush-handles, and grab rails. Even the pens used by the staff are a high-copper brass. A similar ward next door retains its traditional metal fittings and will act as a control in the experiment. If the laboratory results are successfully replicated, it is likely that thousands of hospitals across Europe will introduce copper-alloy fittings.
The Copper Development Assoc. has been working with supply chains to support the development of copper alloy health-care products. Any designer, material supplier, product manufacturer, or researcher with an interest in designing- out infection in hospitals is welcome to join the Antimicrobial Copper Interest Group. Further information on antimicrobial properties of copper can be found at www.cda.org.uk/antimicrobial.
Department of Defense takes aim
Congress recently appropriated funds to the DOD to determine the antimicrobial effectiveness of copper, brass, and bronze. One study will focus on the ability of copper metals to kill deadly pathogens on touch surfaces in New York City and Charleston, S.C., hospitals. The other focus will be copper components in heating, ventilation, and air-conditioning (HVAC) systems at three military installations. The studies will be carried out for the DOD under the aegis of the Telemedicine and Advanced Technologies Research Center (TATRC), a section of the Army Medical Research and Materiel Command (USAMRMC), and implemented by Advanced Technology Institute (ATI).
Microbial growth on common touch surfaces is of increasing concern to health-care facilities. According to Harold Michels, vice president of Technical and Information Services for The Copper Development Assoc., “A positive outcome to these studies will give hospitals solid information on an additional method of reducing infection rates and controlling virulent, antibiotic-resistant pathogens.”
The touch surfaces study will employ a series of three clinical trials to determine how well natural copper, brass, and bronze surfaces mitigate infectious microbes, reduce cross-contamination, and ultimately help minimize the incidence of hospital- acquired infections in patients, says Michels. “Rates of infection will be measured using three indicator organisms: MRSA (Methicillin-resistant Staphylococcus aureus), vancomycin-resistant enterococci (VRE), and acinetobacter baumannii, of particular concern since the beginning of the Iraq War.” People most at risk for difficult-to-treat acinetobacter infections are those with compromised immune systems, traumatic wounds, and those treated in intensive-care units. Surfaces involved in the DOD study are typically made of stainless steel or plastic, which have little or no effect in controlling or inactivating pathogens.
Memorial Sloan-Kettering Cancer Center in New York City, the Medical University of South Carolina, and the Ralph H. Johnson VA Medical Center, both in Charleston, S.C., will conduct the studies. Previous work conducted by ATS Labs, Eagan, Minn., has shown that solid copper alloys are more than 99.9% effective in eliminating five pathogens commonly found in health-care facilities.
The companion HVAC study will compare copper air-conditioning system components, including cooling coils, heat exchange fins, and drip pans, with those made from aluminum. The trials will demonstrate how well copper surfaces reduce the colonization of HVAC systems by harmful bacteria and fungi.
Laboratory studies are taking place at the University of South Carolina. Field trials will be at the Moncrief Army Community Hospital and barracks at Ft. Jackson, the D.D. Eisenhower Army Medical Center at Ft. Gordon, and the U.S. Air Force Academy. “The results of these real-world trials should encourage a leap forward in the design of HVAC systems and make a major contribution to the reduction of Sick Building Syndrome and the improvement of indoor air quality,” says Michels.