Antibacterial efficacy of copper alloy touch surfaces

Copper alloy surfaces have intrinsic properties to destroy a wide range of microorganisms. In the interest of protecting public health, especially in healthcare environments with their susceptible patient populations, an abundance of peer-reviewed antimicrobial efficacy studies have been conducted in the past ten years regarding copper's efficacy to destroy E. coli O157:H7, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus, Clostridium difficile, influenza A virus, adenovirus, and fungi. Stainless steel was also investigated because it is an important surface material in today's healthcare environments. The studies cited here, plus others directed by the United States Environmental Protection Agency, resulted in the 2008 registration of 274 different copper alloys as certified antimicrobial materials that have public health benefits.

Recent studies have shown that copper alloy surfaces kill E. coli O157:H7. More than 99.9% of E. coli microbes are killed after just 1–2 hours on copper. On stainless steel surfaces, the microbes can survive for weeks.

Results of E. coli O157:H7 destruction on an alloy containing 99.9% copper (C11000) demonstrate that this pathogen is rapidly and almost completely killed (more than 99.9% kill rate) within ninety minutes at room temperature (20 °C). At chill temperatures (4 °C), more than 99.9% of E. coli O157:H7 are killed within 270 minutes. E. coli O157:H7 destruction on several copper alloys containing 99%–100% copper (including C10200, C11000, C18080, and C19700) at room temperature begins within minutes. At chilled temperatures, the inactivation process takes about an hour longer. No significant reduction in the amount of viable E. coli O157:H7 occurs on stainless steel after 270 minutes.

Studies have been conducted to examine the E. coli O157:H7 bactericidal efficacies on 25 different copper alloys to identify those alloys that provide the best combination of antimicrobial activity, corrosion/oxidation resistance, and fabrication properties. Copper's antibacterial effect was found to be intrinsic in all of the copper alloys tested. As in previous studies, no antibacterial properties were observed on stainless steel (UNS S30400). Also, in confirmation with earlier studies, the rate of drop-off of E. coli O157:H7 on the copper alloys is faster at room temperature than at chill temperature.

For the most part, the bacterial kill rate of copper alloys increased with increasing copper content of the alloy. This is further evidence of copper's intrinsic antibacterial properties.

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