Nosocomial infections and the emergence of antibiotic-resistant strains pose significant clinical and economic challenges.1,2 While good hygiene practices are the bedrock for infection control, emerging evidence suggests that continuously killing antimicrobial surfaces based on metallic copper can reduce bioburden and lower the risk of infection.3 Copper’s multiple mechanisms of action, which includes the ability to destroy genomic and plasmid DNA,4 explain its longstanding antimicrobial efficacy against pathogens such as antibiotic-resistant “superbugs”.5,6 Proposed mechanisms for copper-mediated cellular damage and toxicity include direct cell membrane damage, the generation of reactive hydroxyl radicals through Fenton-type reactions, and entry of copper ions into cells through ligand interactions, causing disruption of RNA and DNA function.5-7 While the precise mechanism is unclear, Cu1+ ions are considerably more toxic to bacteria than Cu2+ ions under test conditions that mimic microbial contamination on solid surfaces.8-10
There has been a significant focus on metallic copper as an antimicrobial since the U.S. EPA introduced a new test protocol in 2008 that was exclusively passed by copper surfaces.11,12 The U.S. EPA mandated that claims of efficacy against human pathogens could only be obtained for products that pass the standard with the justification that it was a realistic simulation of contamination unlike the traditional test.6,13 We wanted to make a copper-containing additive compatible with commonly used surfaces and coatings that demonstrated the efficacy to kill ≥99.9% of bacteria under EPA’s test conditions retaining copper’s broad spectrum efficacy and low probability for the development of resistant strains.5,14