Effects of temperature and humidity on the efficacy of methicillin-resistant Staphylococcus aureus challenged antimicrobial materials containing silver and copper

Copper Development Association Inc., New York, NY 10016, USA.
Letters in Applied Microbiology (Impact Factor: 1.75). 04/2009; 49(2):191-5. DOI: 10.1111/j.1472-765X.2009.02637.x
Source: PubMed

ABSTRACT To compare silver and copper, metals with known antimicrobial properties, by evaluating the effects of temperature and humidity on efficacy by challenging with methicillin resistant Staphylococcus aureus (MRSA).
Using standard methodology described in a globally used Japanese Industrial Standard, JIS Z 2801, a silver ion-containing material exhibited >5 log reduction in MRSA viability after 24 h at >90% relative humidity (RH) at 20 degrees C and 35 degrees C but only a <0.3 log at approximately 22% RH and 20 degrees C and no reduction at approximately 22% RH and 35 degrees C. Copper alloys demonstrated >5 log reductions under all test conditions.
While the high humidity (>90% RH) and high temperature (35 degrees C) utilized in JIS Z 2801 produce measurable efficacy in a silver ion-containing material, it showed no significant response at lower temperature and humidity levels typical of indoor environments.
The high efficacy levels displayed by the copper alloys, at temperature and humidity levels typical of indoor environments, compared to the low efficacy of the silver ion-containing material under the same conditions, favours the use of copper alloys as antimicrobial materials in indoor environments such as hospitals.

Download full-text


Available from: Charles William Keevil, Aug 12, 2015
  • Source
    • "Even though the antibacterial mechanism of silver is still unclear, it has been proposed that it is a combination of the action of silver ions and particles where the smaller the nanoparticle, the biggest the importance of the activity of silver ions [26]. Humidity is a key factor for ion transportation [27] and the drop of efficacy in antibacterial activity is expected in dry environments according to previous reports [11] [28]. Nevertheless, humidity is not only a pathway for ion transportation, it is also a trigger for silver ions generation [29] "
    [Show abstract] [Hide abstract]
    ABSTRACT: Silver nanoparticles synthesized on titanium dioxide (Ag/TiO2), an effective antibacterial additive, were added to a commercial paint and its antimicrobial activity was evaluated. Microbiological tests against Escherichia coli and Methicillin-resistant Staphylococcus aureus were performed under high relative humidity (RH>90%) and low (RH≈14%). A remarkable difference in cell recovery under high and low humidity was found.
    Materials Letters 11/2014; 134:103–106. DOI:10.1016/j.matlet.2014.07.067 · 2.27 Impact Factor
  • Source
    • "Cu is widely used for its antimicrobial properties (Borkow and Gabbay, 2009; Grass et al., 2011). Cu and Cu alloy surfaces have been shown to kill a variety of pathogens including Salmonella enterica and Campylobacter jejeuni (Faundez et al., 2004), Listeria monocytogenes (Wilks et al., 2006), methicillin resistant Staphylococcus aureus (MRSA; Noyce et al., 2006a; Gould et al., 2009; Michels et al., 2009; Weaver et al., 2010), Escherichia coli O157 (Wilks et al., 2005; Noyce et al., 2006b), Mycobacterium tuberculosis (Mehtar et al., 2008), Clostridium difficile "
    [Show abstract] [Hide abstract]
    ABSTRACT: There is increasing recognition that the healthcare environment acts as an important reservoir for transmission of healthcare acquired infections (HCAI). One method of reducing environmental contamination would be use of antimicrobial materials. The antimicrobial activity of thin silica-copper films prepared by chemical vapour deposition was evaluated against standard strains of bacteria used for disinfectant testing and bacteria of current interest in HCAI. The structure of the coatings was determined using Scanning Electron Microscopy and their hardness and adhesion to the substrate determined. Antimicrobial activity was tested using a method based on BS ISO 22196:2007. The coatings had a pale green-brown colour and had a similar hardness to steel. SEM showed nano-structured aggregates of Cu within a silica matrix. A log10 reduction in viability of >5 could be obtained within 4 h for the disinfectant test strains and within 6 h for producing Acinetobacter baumannii, Klebsiella pneumoniae and Stenotrophomonas maltophilia. Activity against the other hospital isolates was slower but still gave log10 reduction factors of >5 for extended spectrum beta-lactamase producing Escherichia coli and >3 for vancomycin resistant Enterococcus faecium, methicillin resistant Staphylococcus aureus and Pseudomonas aeruginosa within 24 h. The results demonstrate the importance of testing antimicrobial materials destined for healthcare use against isolates of current interest in hospitals as well as standard test strains. The coatings used here can also be applied to substrates such as metals and ceramics and have potential applications where reduction of microbial environmental contamination is desirable.
    09/2013; 3(1):53. DOI:10.1186/2191-0855-3-53
  • Source
    • "In our hands, silver surfaces did not kill bacteria (Nies and Nies, unpublished observations). In line with this observation, copper alloys indeed were much more efficient as antimicrobial materials than silver-containing materials at temperature and humidity levels typical for indoor environments such as hospitals (Michels et al. 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Basic chemistry of copper is responsible for its Janus-faced feature: on one hand, copper is an essential trace element required to interact efficiently with molecular oxygen. On the other hand, interaction with reactive oxygen species in undesired Fenton-like reactions leads to the production of hydroxyl radicals, which rapidly damage cellular macromolecules. Moreover, copper cations strongly bind to thiol compounds disturbing redox-homeostasis and may also remove cations of other transition metals from their native binding sites in enzymes. Nature has learned during evolution to deal with the dangerous yet important copper cations. Bacterial cells use different efflux systems to detoxify the metal from the cytoplasm or periplasm. Despite this ability, bacteria are rapidly killed on dry metallic copper surfaces. The mode of killing likely involves copper cations being released from the metallic copper and reactive oxygen species. With all this knowledge about the interaction of copper and its cations with cellular macromolecules in mind, experiments were moved to the next level, and the antimicrobial properties of copper-containing alloys in an "everyday" hospital setting were investigated. The alloys tested decreased the number of colony-forming units on metallic copper-containing surfaces by one third compared to control aluminum or plastic surfaces. Moreover, after disinfection, repopulation of the surfaces was delayed on copper alloys. This study bridges a gap between basic research concerning cellular copper homeostasis and application of this knowledge. It demonstrates that the use of copper-containing alloys may limit the spread of multiple drug-resistant bacteria in hospitals.
    Applied Microbiology and Biotechnology 05/2010; 87(5):1875-9. DOI:10.1007/s00253-010-2640-1 · 3.81 Impact Factor
Show more