Biocidal Efficacy of Copper Alloys against Pathogenic Enterococci Involves Degradation of Genomic and Plasmid DNAs

Abstract

The increasing incidence of nosocomial infections caused by glycopeptide-resistant enterococci is a global concern. Enterococcal species are also difficult to eradicate with existing cleaning regimens; they can survive for long periods on surfaces, thus contributing to cases of reinfection and spread of antibiotic-resistant strains. We have investigated the potential use of copper alloys as bactericidal surfaces. Clinical isolates of vancomycinresistant Enterococcus faecalis and Enterococcus faecium were inoculated onto copper alloy and stainless steel surfaces. Samples were assessed for the presence of viable cells by conventional culture, detection of actively respiring cells, and assessment of cell membrane integrity. Both species survived for up to several weeks on stainless steel. However, no viable cells were detected on any alloys following exposure for 1 h at an inoculum concentration of <10 4 CFU/cm 2 . Analysis of genomic and plasmid DNA from bacterial cells recovered from metal surfaces indicates substantial disintegration of the DNA following exposure to copper surfaces that is not evident in cells recovered from stainless steel. The DNA fragmentation is so extensive, and coupled with the rapid cell death which occurs on copper surfaces, that it suggests that mutation is less likely to occur. It is therefore highly unlikely that genetic information can be transferred to receptive organisms recontaminating the same area. A combination of effective cleaning regimens and contact surfaces containing copper could be useful not only to prevent the spread of viable pathogenic enterococci but also to mitigate against the occurrence of potential resistance to copper, biocides, or antibiotics and the spread of genetic determinants of resistance to other species.

Lack of Involvement of Fenton Chemistry in Death of Methicillin-Resistant and Methicillin-Sensitive Strains of Staphylococcus aureus and Destruction of Their Genomes on Wet or Dry Copper Alloy Surfaces

“…The stain will not bind to degraded nucleic acid. Metal coupons were inoculated as described for culture assessment and were stained in situ as described previously (14). Briefly, cells were dually stained with 5 mM CTC and 5 M SYTO 9 for the final 90 and 30 min of the tested 2-h contact time, respectively.…”

“…In this study, we investigated the abilities of several copper alloys to kill MRSA and MSSA and the mechanism of bacterial death on surfaces contaminated by simulated droplet and fingertip touch. (Table 1) and were cut into coupons (10 by 10 by 0.5 mm) that were cleaned and sterilized as described previously (14).…”

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

“…The bacterial reduction under light irradiation used a Philips Master-18W/865 lamp (4.65 mW/cm 2 ). The relevance of TiO2-Cu catalysts and photocatalysts addressing the issue of bacterial inactivation is reflected in the increasing number of studies focusing on the antibacterial effects of TiO2-Cu and TiO2/Cu in the form of 2D-coatings, suspensions, spheres, alloys, and decorated binary oxides [175][176][177][178][179][180][181].…”