Mechanism of Copper Surface Toxicity in Vancomycin-Resistant Enterococci following Wet or Dry Surface Contact

Abstract

Contaminated touch surfaces have been implicated in the spread of hospital-acquired infections, and the use of biocidal surfaces could help to reduce this cross-contamination. In a previous study we reported the death of aqueous inocula of pathogenic Enterococcus faecalis or Enterococcus faecium isolates, simulating fomite surface contamination, in 1 h on copper alloys, compared to survival for months on stainless steel. In our current study we observed an even faster kill of over a 6-log reduction of viable enterococci in less than 10 min on copper alloys with a "dry" inoculum equivalent to touch contamination. We investigated the effect of copper(I) and copper(II) chelation and the quenching of reactive oxygen species on cell viability assessed by culture and their effects on genomic DNA, membrane potential, and respiration in situ on metal surfaces. We propose that copper surface toxicity for enterococci involves the direct or indirect action of released copper ionic species and the generation of superoxide, resulting in arrested respiration and DNA breakdown as the first stages of cell death. The generation of hydroxyl radicals by the Fenton reaction does not appear to be the dominant instrument of DNA damage. The bacterial membrane potential is unaffected in the early stages of wet and dry surface contact, suggesting that the membrane is not compromised until after cell death. These results also highlight the importance of correct surface cleaning protocols to perpetuate copper ion release and prevent the chelation of ions by contaminants, which could reduce the efficacy of the surface.

Cicada Wing Surface Topography: An Investigation into the Bactericidal Properties of Nanostructural Features

“…7 Of the different novel strategic designs, surfaces capable of releasing antibiotics have shown to display effective bactericidal properties; however these have been shown to possess a number of disadvantages including long leaching times, lack of control of concentration upon delivery, and poor durability. [8][9][10][11][12] Consequently, an approach driven by a mechanism that is independent from existing conventional methods is of high importance, especially one based on the material's inherent properties, which would push new frontiers in antibacterial surface design. Hence, much attention has shifted to what the natural world has to offer by reverse-engineering bio-inspired antibacterial surface solutions.…”

Disastrous performance of NanoCote/Aqua Based antimicrobial paint in a hospital setting

“…In recent years considerable progress has been made towards elucidating the bactericidal mechanism of copper [21][22][23][24][25][26][27]. There is no need to discuss it here, 1 other than to remark that the release of copper ions from the surface is required, hence the encapsulation matrix should be chosen so as to allow their (slow) release.…”

Recent Developments in Accelerated Antibacterial Inactivation on 2D Cu-Titania Surfaces under Indoor Visible Light

“…In the last decade, Cu has been widely reported to increase the bactericidal activity of TiO 2 [13,22,42,43,56,64,94,[112][113][114][115][132][133][134][135][136][137][138][139][140][141][142]153]. This section presents some relevant developments (and references) of work regarding bacterial inactivation mediated by TiO 2 /Cu powders and TiO 2 /Cu surfaces by catalysis and photocatalysis.…”

“…The inactivation of Vancomycin resistant enterococci (VRE) and MRSA isolates is important due their strong infectious effects and the fact that they can survive for months in health facilities [6][7][8][9][10][11][12][13][14][23][24][25][26]. The inactivation of multidrug-resistant (MDR) pathogens such as Gram-positive, Gram-negative, or fungi on Cu-polyester (Cu-PES) has been reported [132,133]. The DCMS of Cu was carried out on polyester (PES) for different times and led to uniform adhesive Cu nanoparticulate films.…”

“…The infections caused by staphylococci, such as Staphylococcus aureus, are problematic in the case of methicillin-resistant S. aureus (MRSA) [145]. Polyurethane catheters currently used in Swiss hospitals do not generally have an infection during the first day, but are prone to infections when used for longer hospital periods [23][24][25]100,112,133,135]. Catheters (being 3D-objects) were sputtered by Ag-Cu and the substrate/sputtered film was maintained under a negative bias of 100-200 V. The Ag/Cu-coatings sputtered led to a faster bacterial inactivation compared to either Ag or Cu by themselves.…”