Antimicrobial Alloys

Brass Against Bacteria

Brass is the well-known alloy of copper and zinc, a favorite of Victorian engineers and modern-day steampunk fans. It was the “go to” alloy when we didn’t want a spark in an era before the widespread use of steel. Of course, it is not pure copper and zinc, it can contain aluminum, arsenic, manganese, and phosphorus and have a varying formula that deviates from the “three parts copper to two parts zinc” standard. I recently re-learned that brass is not only a non-sparking alloy, it is also an antimicrobial material.

It is the copper that endows brass with its microbicidal properties and it is lethal to many pathogens within minutes or hours depending on germ abundance. Although we had known this for centuries, it was not until 1983 that Phyllis J. Kuhn published details of the antibacterial effects of brass doorknobs [1]. The copper causes damage to the bacteria’s membrane, which kills them.

Antimicrobial Applications

Now, I thought I’d had a novel brainwave: In this age of bacterial resistance and hospital superbugs, might we not take a leaf from the steampunk manual and refit hospital doors, beds, and rails, food trays, and other equipment with brass handles to help halt the spread of MRSA (methicillin-resistant Staphylococcus aureus), C. diff (Clostridium difficile), and their ilk? Well, it seems that in 2007, US Department of Defense’s Telemedicine and Advanced Technology Research Center (TATRC) had already had this thought and tested copper alloys for replacement fittings in several hospitals with great success, particularly in intensive care units.

Preliminary data published in 2011 revealed that the “coppered” hospital rooms had a 97 % reduction in pathogen levels compared to standard rooms [2]. More importantly though, this translated to a reduction in hospital-acquired infections (40 % lower risk), a leading cause of subsequent morbidity and mortality in patients. The critical point to note is that bacteria are unlikely to resist the lethality of sufficient copper; it will, so to speak, always burst their bubble.

A quick scan of the biomedical literature reveals that copper alloys are being investigated widely now for antibacterial applications [3–6]. Titanium and other metals have also been investigated as alternative alloying metals to the zinc in our old friend brass. It seems that coppering up and not relying on stainless steel and plastics, which mostly lack antibacterial activity, could be the way forward.

References