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: 1.66). 04/2009; 49(2):191-5. DOI: 10.1111/j.1472-765X.2009.02637.x
Source: PubMed


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
  • Source
    • "Many variables can influence the survival capacity of microorganisms make it difficult to understand more deeply the contribution of contaminated inert materials to their transmission (Mariscal et al., 2011). An essential condition is the environmental humidity degree and the temperature (Michels et al., 2009). While our in vitro test was carried out at 30°C with a humidity steadily greater than 70%, measured with a hygrometer, in the test on the uniforms worn the temperature and the humidity degree were not always constant and generally much lower; probably the silver doped uniforms for these reasons were unable to show the expected antimicrobial activity. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Among several alternatives to control hospital-acquired infections (HAIs), a strategy could be the use of hospital uniforms imbued with antimicrobial substances. For this purpose we evaluated the antibacterial activity of two different silver doped fabrics employed for the production of hospital uniforms. The study was conducted in two-step. In the first the antimicrobial activity was evaluated in vitro against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 6538, Enterococcus faecalis ATCC 29212. In the second, we tested the total viable counts detected from beginning to end of the work shift on experimental silver doped uniforms worn by doctors, nurses, allied health assistants in different hospital wards. The in vitro tests showed a remarkable antibacterial activity of both silver doped samples (>99.9% reduction within 4h of exposure for Gram-positive and within 24h for Gram-negative bacteria). The experimental uniforms provided results only slightly in agreement with in vitro data. Even if the increase of total viable counts was somewhat lower for experimental uniforms than traditional ones, significant differences were not observed. Despite the results on the uniforms worn, the addition of silver in fabrics to make medical equipment (supplies) remains an interesting option for HAI control.
    Full-text · Article · Oct 2015 · The New Microbiologica: official journal of the Italian Society for Medical Virology (SIVIM)
  • 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.
    Full-text · Article · Nov 2014 · Materials Letters
  • 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.
    Full-text · Article · Sep 2013 · AMB Express
Show more