Survival of MRSA attached to materials used in medical facilities at different humidity levels

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) attached to materials and equipmentused in medical facilities reportedly survives for several weeks under normal conditions.According to our survival studies on pieces of silicone rubber, silver, aluminum, andstainless steel at 20°C, methicillin-sensitive Staphylococcus aureus [MSSA (ATCC29213)],MRSA (ATCC43300), and environment-origin MRSA (L1) all survived after 30 days. Onsilver, however, there have been conflicting reports concerning the survival in environmentsat different humidity levels. In this study, we evaluated the survivability of S. aureus on thebed railing and linen used at medical facilities at 20°C under different humidity conditions.The survival rates of bacteria at 88.7% RH (83.3-94.7% ; high humidity) and 47.9% RH(38.1-57.6% ; low humidity) were compared after culturing for 1, 2, 3, 7, 15, and 30 days onsome metal or non metal materials.On pieces of copper and brass, MSSA, MRSA, and MRSA (L1) did not survive longerthan 1 day at either the high or low humidity. On pieces of silver, aluminum, and stainlesssteel, MSSA, MRSA, and MRSA (L1) survived for longer at the low compared to thehigh humidity. On silver, which is considered to exhibit antimicrobial activity, S. aureus isbelieved to survive for a long period in seasons with a low relative humidity, and appropriateanti-infection measures should be practiced without overconfidence in their antimicrobialeffects.