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Antimicrobial Metals Keep Microbes Under Control

Emerging antibiotic resistant pathogens is a topic that causes universal anxiety. In the U.S., these types of infections are responsible for more deaths than AIDS. Thanks to the media, we have been lead to believe that MRSA, Methicillin-resistant Staphylococcus aureus, lurks on every public doorknob. Although it is present in some public facilities (it is sometimes found in locker rooms and gyms), there is good news. Individuals with a healthy immune system may unknowingly carry MRSA for weeks or years without ill effect. Mostly, infection from MRSA is a threat for patients in the healthcare system.

 

Hospital patients with one of these "superbug" infections have a five-fold greater risk of death than those without. There is no drug of choice for treatment. Even with the most powerful antibiotics, options are limited. Until patients can be effectively treated for MRSA, the best course of action is to not contract an infection in the first place.

 

Studies have shown that 80% of infectious diseases are transferred by touch.

 

A virus-contaminated hand can spread virulent pathogens to the next several surfaces it touches. The medical  community can promote the use of anti- microbial soaps, but healthcare personnel can't be convinced to wash their hands more frequently. Sprayed and wiped disinfectants can effectively clean surfaces, but the killing power of these agents does not last. Hard surfaces can easily be contaminated again.

 

Anti-microbial additives for plastics have been available for quite some time, and the organic substance triclosan (widely marketed at Microban™) is the one most widely used. There are a couple of drawbacks hindering its use more extensively. As an organic compound, it is deactivated under the high temperatures required for processing some resins. It is also possible (though still debatable) that triclosan leaching into the environment could allow resistant strains of microbes to develop. On the plus side it is inexpensive compared to other antimicrobial additives, so the substance is routinely used for commodity consumer goods and disposable products. The bottom line is that even though organic additives have their place, there may be a better way to control the spread of infection. 

 

Designers can help to lower the incidence of hospital-acquired infections (HAIs) by specifying materials that are anti-microbial by nature.

 

Copper and silver have been recognized as germ killers for literally thousands of years. The Egyptians and Romans didn't know about microbes, but they used silver surgical instruments to limited infection, copper coins to purify water and copper-threaded textiles to sterilize wounds.

 

In 2008 the US Environmental Protection Agency approved 282 copper alloys to be registered as antimicrobial agents. Copper and its alloys are the first solid materials to acquire this status. Tests have demonstrated that 99.9% of bacteria on copper alloy surfaces, those with greater than 65% copper content, were killed within two hours. The bactericidal action is effective against MRSA, Influenza H1N1, E. coli 0157, and a wide range of other dangerous pathogens, including viruses. It should be noted that these alloys are effective germ killers even at room temperature and under typical indoor humidity conditions.

 

The bactericidal action of silver ions has proven useful for alternate applications compared to copper.

 

Silver ion containing materials can be readily added to plastics and incorporated into coatings. As a plastic additive, silver exhibits high thermal stability, a significant benefit in plastic forming and manufacturing processes that require high temperatures, up to 500 degrees C. Silver is non-toxic, and provides long-term protection, but one drawback is its subpar performance under low humidity conditions – there must be moisture present for silver-based materials to release their bacteria killing ions. Silver ions also loose their effectiveness at room temperature. These two properties make antimicrobial silver additives and coatings mainly suited for catheters, respiratory tubes, and wound dressing textiles – still, the three major sources of hospital acquired infections.

 

For hard surfaces, nothing beats copper. It is safe, long lasting, and effective at wide temperature ranges against most of the most important microbes, fungi, and protozoans, and because of copper's mode of action, bacteria cannot develop a resistance. Hospitals in the US, UK, Japan, and Germany are conducting use trials by replacing surfaces usually made of stainless steel (where bacterial can live for weeks) with alloys containing a high copper content. Potential touch surfaces that act as reservoirs of infection are door knobs, water fixtures, push and switch plates, bed rails, drawer pulls, and toilet seats. Reports state that the use of these alloys can reduce the microbial load on potentially contaminated surfaces by 90 to 100%.

 

High-copper alloys are available in a palette of colors, not only a variation of red we usually associate with the element. The "silver" coins in your pocket – the dimes, quarters, and half-dollars are surfaced with an alloy of 75% copper and 25% nickel. Our "gold" dollar coins consist of 88.5% copper. Contrary to what we have been led to believe, coins are not always covered with germs. According to laboratory tests, if U.S. coins are free from dirt and grime, E. coli, MRSA, and other bacteria will die on their surfaces in less than an hour.

 

In the future, expect to see more hospital and consumer fixtures touting the benefits of "antimicrobial copper". For designers, it is poised to make a significant impact in the campaign against dreaded MRSA and other hospital-acquired infections.