Abstract
Copper (Cu) and its alloys have bactericidal activity known as “contact killing” with degradation of nucleic acids inside the bacteria, which is beneficial to inhibit horizontal gene transfer (HGF). In order to understand the nucleic acid degradability of Cu and its alloy surfaces, we developed a new in vitro method to quantitatively evaluate it by a swab method under a “dry” condition and compared it with that of commercially available antibacterial materials such as antibacterial stainless steel, pure silver, and antibacterial resins. As a result, only Cu and its alloys showed continuous degradation of nucleic acids for up to 6 h of contact time. The nucleic acid degradability levels of the Cu alloys and other antibacterial materials correlate to their antibacterial activities evaluated by a film method referring to JIS Z 2801:2012 for Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Nucleic acid degradation by copper (I) and (II) chlorides was confirmed at the ranges over 10 mM and 1–20 mM, respectively, suggesting that the copper ion release may be responsible for the degradation of the nucleic acids on Cu and its alloy surfaces. In conclusion, the higher Cu content in the alloys gave higher nucleic acid degradability and higher antibacterial activities.
Highlights
Antimicrobial resistance (AMR) in bacteria has become a global threat, and deaths attributable to AMR are estimated to reach over 10 million people by 2050 [1]
Contaminated touch surfaces in hospital rooms play an important role in the transmission of healthcare-associated pathogens [2], it is important to control the number of viable bacteria on touch surfaces, since methicillin-resistant Staphylococcus aureus (MRSA), one of the causes of healthcareassociated infection (HAI) in hospitals, can survive for months with infectivity on general touch surfaces of resin and stainless steel [3]
The remaining nucleic acid in the swab was further extracted into the solvent and quantified using a fluorescent die, acridine orange (AO), a nucleic acid intercalater
Summary
Antimicrobial resistance (AMR) in bacteria has become a global threat, and deaths attributable to AMR are estimated to reach over 10 million people by 2050 [1]. Contaminated touch surfaces in hospital rooms play an important role in the transmission of healthcare-associated pathogens [2], it is important to control the number of viable bacteria (bioburden) on touch surfaces, since methicillin-resistant Staphylococcus aureus (MRSA), one of the causes of healthcareassociated infection (HAI) in hospitals, can survive for months with infectivity on general touch surfaces of resin and stainless steel [3]. Under these circumstances, metal copper and its alloys have attracted attention in healthcare-related fields due to their excellent antimicrobial activity. Copper and its alloys containing copper with over 60% in their composition were registered at the US Environmental
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