Contact Killing of Bacteria on Copper Is Suppressed if Bacterial-Metal Contact Is Prevented and Is Induced on Iron by Copper Ions

Mathews, Salima; Hans, Michael; Mücklich, Frank; Solioz, Marc

doi:10.1128/aem.03608-12

Cited by 161 publications

(129 citation statements)

References 43 publications

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“…The second important requirement for contact killing is bacterial contact with the metal surface (16). Recently, we showed that bacteria are also killed effectively on iron surfaces if ionic copper ions are present (16). In the present study, we also show that the reduction of Cu 2ϩ to Cu ϩ by the iron surface plays a key role in the killing process.…”

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Copper Reduction and Contact Killing of Bacteria by Iron Surfaces

Mathews

Kumar

Solioz

2015

Appl Environ Microbiol

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Federation bThe well-established killing of bacteria by copper surfaces, also called contact killing, is currently believed to be a combined effect of bacterial contact with the copper surface and the dissolution of copper, resulting in lethal bacterial damage. Iron can similarly be released in ionic form from iron surfaces and would thus be expected to also exhibit contact killing, although essentially no contact killing is observed by iron surfaces. However, we show here that the exposure of bacteria to iron surfaces in the presence of copper ions results in efficient contact killing. The process involves reduction of Cu 2؉ to Cu ؉ by iron; Cu ؉ has been shown to be considerably more toxic to cells than Cu 2؉ . The specific Cu ؉ chelator, bicinchoninic acid, suppresses contact killing by chelating the Cu ؉ ions. These findings underline the importance of Cu ؉ ions in the contact killing process and infer that ironbased alloys containing copper could provide novel antimicrobial materials.T he killing of bacteria by metallic copper surfaces, so-called "contact killing," is now well established and has explicitly been shown for many species (1). Bacteria are killed within minutes on surfaces of copper or copper alloys containing at least 60% copper. In contrast, cells can survive for days on surfaces of stainless steel, glass, or plastics. Copper and copper alloys have attracted attention as a means of creating self-sanitizing surfaces in the light of increasing nosocomial infections in Western hospitals. In a number of hospital trials, rooms have been fitted with copper alloy table tops, bedrails, door handles, light switches, bathroom fixtures, etc., in an effort to curb nosocomial infections (2-5; K. Laitinen et al., unpublished data). These copper surfaces resulted in a 2-to 3-log reduction of the microbial burden on a continuous basis. However, further data are needed to convincingly demonstrate that these measures also lead to a lasting reduction of nosocomial infections. Nevertheless, it appears clear that copper-containing materials can contribute to hospital hygiene and lower the bacterial burden also in other facilities where clean or aseptic working procedures are required (6).The mechanism of contact killing of bacteria by coppercontaining materials is of interest not only in connection to its use in hospitals but also from a purely scientific point of view. Laboratory studies have shown that bacteria on copper surfaces suffer rapid membrane damage and DNA degradation, in addition to other less well-defined cellular damage (7-12). The importance and the order of the different processes leading to cell death may depend on the type of microorganism (9). One key element required for contact killing is the release of copper ions from the metal surface. Bacterial copper resistance systems appear unable to cope with the released copper (13-15). The second important requirement for contact killing is bacterial contact with the metal surface (16). Recently, we showed that bacteria are also killed effectively ...

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“…Bacterial copper resistance systems appear unable to cope with the released copper (13)(14)(15). The second important requirement for contact killing is bacterial contact with the metal surface (16). Recently, we showed that bacteria are also killed effectively on iron surfaces if ionic copper ions are present (16).…”

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Copper Reduction and Contact Killing of Bacteria by Iron Surfaces

Mathews

Kumar

Solioz

2015

Appl Environ Microbiol

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“…This effect has been demonstrated for bacteria such as pathogenic Escherichia coli strains (4), Pseudomonas aeruginosa (5), methicillin-resistant Staphylococcus aureus (6), Burkholderia cepacia (7), and Salmonella enterica (8), as well as for viruses (9,10) and yeasts (11). Copper ions need to be released from the copper surfaces to mediate the killing process (12,13), and there has to be direct contact between the cell and the copper surface (14). Therefore, a variety of parameters influence the success of the inactivation process by interfering with copper release and the availability of the copper ions for the killing action: (i) temperature, (ii) humidity, (iii) ionization/corrosion, (iv) the dry/ wet test protocol used, and (v) the content of organic material (6,15,16).…”

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Survival of Escherichia coli Cells on Solid Copper Surfaces Is Increased by Glutathione

Große

Schleuder

Schmole

et al. 2014

Appl Environ Microbiol

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Bacteria are rapidly killed on solid copper surfaces, so this material could be useful to limit the spread of multiple-drug-resistant bacteria in hospitals. In Escherichia coli, the DNA-protecting Dps protein and the NADH:ubiquinone oxidoreductase II Ndh were not involved in tolerance to copper ions or survival on solid copper surfaces. Decreased copper tolerance under anaerobic growth conditions in the presence of ascorbate and with melibiose as the carbon source indicated that sodium-dependent symport systems may provide an import route for Cu I into the cytoplasm. Glutathione-free ⌬copA ⌬gshA double mutants of E. coli were more rapidly inactivated on solid copper surfaces than glutathione-containing wild-type cells. Therefore, while DNA protection by Dps was not required, glutathione was needed to protect the cytoplasm and the DNA against damage mediated by solid copper surfaces, which may explain the differences in the molecular mechanisms of killing between glutathione-containing Gram-negative and glutathione-free Gram-positive bacteria.

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“…The limited data so far available suggest only modest antimicrobial action. Mathews et al emphasized the need of the bacteria to be in contact with the copper if killing is to occur [27]. Nevertheless, the polyacrylic material used in NanoCote HD-WR may be sufficiently permeable to allow copper to be present at the surface on which the bacteria will arrive.…”

Section: Coefficients Of Friction In the Wet And Dry Statesmentioning

confidence: 99%

“…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.…”

Section: Disastrous Performance Of Nanocote/aqua Based Antimicrobial mentioning

confidence: 99%

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

Ramsden¹,

Reid²,

Whatley³

et al. 2016

JBPC

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Attempts are being made to incorporate copper into clear varnish in order to coat environmental surfaces in hospitals with the long-term goal of reducing healthcare-acquired infections (HAI). The performance of a nanocopper-containing polyacrylic emulsion, NanoCote HD-WR, on bedrails, footboards, control panels, tables and lockers was evaluated. The paint was applied in four coats using conventional spraying technology according to the manufacturer's instructions to give a total thickness of c. 30 µm. After overnight curing the "clear" coat appeared rough, with uneven mottling, and remained clearly visible on all surfaces to which it had been applied. The coating demonstrated an unpleasant rubbery feel, engendering complaints from patients. Even the merest contact with water, such as light touching with a damp cloth, caused immediate blanching of the coating and the surface became extremely slippery. Contact with a lightly soiled cloth caused irreversible discoloration of the coating. The physical properties of this coating render it unacceptable for application in hospitals.

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Contact Killing of Bacteria on Copper Is Suppressed if Bacterial-Metal Contact Is Prevented and Is Induced on Iron by Copper Ions

Cited by 161 publications

References 43 publications

Copper Reduction and Contact Killing of Bacteria by Iron Surfaces

Copper Reduction and Contact Killing of Bacteria by Iron Surfaces

Survival of Escherichia coli Cells on Solid Copper Surfaces Is Increased by Glutathione

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

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