Potential action of copper surfaces on meticillin-resistant Staphylococcus aureus.

AIMS: Studies to date have shown rapid killing of bacterial cells when exposed to copper surfaces. The mechanistic action of copper on bacterial cells is so far unknown. METHODS AND RESULTS: To investigate potential mechanisms involved, meticillin-resistant Staphylococcus aureus (MRSA) cells (10(7) CFU) were inoculated onto coupons of copper or stainless steel and stained with either the viability fluorophore 5-cyano-2,3-ditolyl tetrazolium (CTC), to detect respiration, or BacLight™ (SYTO9/propidium iodide), to determine cell wall integrity. Coupons were then observed in-situ using epifluorescence microscopy. In addition, DNA from cells inoculated onto either copper or stainless steel surfaces was isolated and analysed by agarose gel electrophoresis. An effect on cellular respiration with CTC reduction was evident but no effect on cell membrane integrity (BacLight™) was observed. Results from the DNA isolation indicated a copper-induced detrimental effect on MRSA genomic material as no bands were observed after exposure to copper surface. CONCLUSIONS: The results indicate that exposure to copper surfaces rapidly kills MRSA by compromising cellular respiration and damaging DNA, with little effect on cell membrane integrity. SIGNIFICANCE AND IMPACT OF THE STUDY: This research provides a mechanistic explanation in support of previous suggestions that although copper surfaces do not affect membrane integrity of cells, there is still a rapid antimicrobial effect.

Biocidal efficacy of copper alloys against pathogenic enterococci involves degradation of genomic and plasmid DNAs.

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 vancomycin-resistant 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

Potential for preventing spread of fungi in air-conditioning systems constructed using copper instead of aluminium.

AIMS: As copper has been previously suggested as an antimicrobial surface, we tested the effectiveness of copper as an antifungal surface which could be used in air-conditioning systems as an alternative to aluminium. METHODS AND RESULTS: Coupons of copper (C11000) and aluminium were inoculated with fungal isolates (Aspergillus spp., Fusarium spp., Penicillium chrysogenum and Candida albicans) for various time periods. Culture on potato dextrose agar and an in situ viability assay using the fluorochrome FUN-1 were used to determine whether spores had survived. The results showed increased die off of fungal isolates tested compared to aluminium. In addition, copper also prevented the germination of spores present, thereby reducing the risk of the release of spores. CONCLUSIONS: Copper offered an antifungal surface and prevented subsequent germination of spores present. FUN-1 demonstrated that fungal spores entered into a viable but not culturable (VBNC) state on copper indicating the importance of using such methods when assessing the effect of an antifungal as culture alone may give false results. SIGNIFICANCE AND IMPACT OF STUDY: Copper offers a valuable alternative to aluminium which could be used in air-conditioning systems in buildings, particularly in hospital environments where patients are more susceptible to fungal infections.

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

AIMS: 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). METHODS AND RESULTS: 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. CONCLUSIONS: 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. SIGNIFICANCE AND IMPACT OF THE STUDY: 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.

Survival of Clostridium difficile on copper and steel: futuristic options for hospital hygiene.

Clostridium difficile is rapidly becoming a major cause of hospital-acquired infections worldwide, due in part to transmission of the faecal pathogen between contaminated hands and contact surfaces. Accordingly, this study evaluated survival of C. difficile vegetative cells and spores on the contact surface commonly found in healthcare settings, stainless steel, compared to five copper alloys (65-100% copper content). C. difficile requires prolonged incubation to grow and therefore the total number and number of viable cells was estimated using a fluorescence dual-staining technique. For viability assessment the redox dye 5-cyano-2,3-ditolyl tetrazolium (CTC) was used to measure metabolic activity. Results demonstrated that copper alloys with a copper content >70% provide a significant reduction in survival of C. difficile vegetative cells and spores on copper alloys compared with stainless steel. Complete death of spores was observed after 24-48 h on copper alloys whereas no significant death rate was observed on stainless steel even after 168 h. The use of CTC gave comparable results to culture and offers a more rapid viability analysis (8 h) than culture. The results suggest that using copper alloys in hospitals and other healthcare facilities could offer the potential to reduce spread of C. difficile from contaminated surfaces.