Environmental study of a methicillin-resistant Staphylococcus aureus epidemic in a burn unit

During an outbreak of infections caused by methicillin-resistant (MR) Staphylococcus aureus in our burn unit, we conducted an extensive 10-week study to define the environmental epidemiology of the organism. The inanimate environment in patient rooms and adjacent areas was examined by using volumetric air samplers and Rodac plates. Airborne and surface level contamination with MR S. aureus was quantitated, and overall, MR S. aureus comprised 16, 31, and 40% of all bacterial growth from air, elevated surfaces, and floor surfaces, respectively. Mean air, elevated surface, and floor surface MR S. aureus contamination in rooms of MR S. aureus-infected burn patients were 1.9 MR S. aureus per ft3 (ca. 0.028 m3), 20 MR S. aureus per Rodac plate and 48 MR S. aureus per Rodac plate, respectively. Peak patient room environmental contamination levels were 6.9 MR S. aureus per ft3 of air, 70 MR S. aureus per Rodac plate per elevated surface and 138 MR S. aureus per Rodac plate per floor surface. Environmental contamination levels in the adjacent work areas were considerably lower than in infected patient rooms. There was ample opportunity for contamination of personnel through the inanimate environment in this unit.