Abstract
The antibacterial efficacy of a copper–silver alloy coating under conditions resembling build up of dry surface bacterial biofilms is successfully demonstrated according to US EPA test methods with a ≥99.9% reduction of test organisms over a 24 h period. A tailor‐made confocal imaging protocol is designed to visualize in situ the killing of bacterial biofilms at the copper–silver alloy surface and monitor the kinetics for 100 min. The copper–silver alloy coating eradicates a biofilm of Gram‐positive bacteria within 5 min while a biofilm of Gram‐negative bacteria are killed more slowly. In situ pH monitoring indicates a 2‐log units increase at the interface between the metallic surface and bacterial biofilm; however, the viability of the bacteria is not directly affected by this raise (pH 8.0–9.5) when tested in buffer. The OH− production, as a result of the interaction between the electrochemically active surface and the bacterial biofilm under environmental conditions, is thus one aspect of the contact‐mediated killing of the copper–silver alloy coating and not the direct cause of the observed antibacterial efficacy. The combination of oxidation of bacterial cells, release of copper ions, and local pH raise characterizes the antibacterial activity of the copper–silver alloy‐coated dry surface.
Highlights
The initial concentration of test organisms was ≈108 CFU mL−1 (Table 1) in line with the United States Environmental Protection Agency (US EPA) Test methods for Efficacy as Sanitizer (Protocol 1) and Continuous Reduction of Bacterial Contamination (Protocol 2) of Copper Alloy Surfaces.[9,10]
ATCC 6538 and Staphylococcus aureus Methicillin Resistant Staphylococcus aureus (MRSA) ATCC 33592 were effectively inactivated by the copper–silver alloy coating with a 5-log reduction compared to the stainless steel control carriers after 2 h (Protocol 1) and at all time points over the 24 h time interval (Protocol 2), yielding a percent reduction greater than 99.9% (Table 1).[9]
In Protocol 1 Pseudomonas aeruginosa ATCC 15442 was able to survive on copper–silver alloy-coated surfaces to a geometric mean of 5.9 CFU per carrier, the percent reduction was 99.9% compared to the stainless steel control surfaces, where the geometric mean of surviving P. aeruginosa was 1.1 × 104 CFU per carrier
Summary
T. Bjarnsholt Department of Clinical Microbiology Rigshospitalet Juliane Maries vej 22, 2100 Copenhagen Ø, Denmark potentially alleviating the occurrence of hospital mediated infections.[4,5,6] Evidence of their antibacterial properties from laboratory experiments has led to several field test studies in healthcare facilities in Europe and USA to validate their performances in real-life conditions.[5,7,8] In 2015, the United States Environmental Protection Agency (US EPA) released tailored protocols for testing and evaluating the antibacterial efficacy of copper and copper alloy surfaces with the intention of providing harmonized test conditions closely resembling real-life applications of such surfaces, e.g., environmental indoor items in healthcare facilities.[9,10,11] The first two protocols allow evaluation of the sanitizing efficacy of copper alloys on test organisms after 2 h exposure and after a prolonged exposure to a bacterial contamination accumulated over a 24 h interval.[9,10] Several copper-based surfaces have demonstrated antimicrobial effectiveness according to these protocols.[12,13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
