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 center dot 3 log at similar to 22% RH and 20 degrees C and no reduction at similar to 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.