Importance of the environment for patient acquisition of methicillin-resistant Staphylococcus aureus in the intensive care unit: A baseline study

OBJECTIVE: To assess the degree of environmental contamination with methicillin-resistant Staphylococcus aureus (MRSA) in critical care and the likelihood of subsequent new patient acquisition if carriers were or were not moved to single rooms. DESIGN: Randomized sequential sampling of bed areas. SETTING: Intensive care units of two teaching hospitals. PATIENTS: Medical and surgical patients requiring critical care. INTERVENTIONS: Six environmental sites around randomly selected patients plus two communal sites were sampled using contact plates during periods when patients with MRSA were physically isolated or not. Admission, weekly, and discharge screening patient swabs were taken to identify patients admitted with, or newly acquiring, MRSA. MEASUREMENTS AND MAIN RESULTS: A total of 2,436 samples were taken from environments around 114 patients, plus a further 349 samples from doctors' hands and telephones. Of the 47 bed areas where MRSA strains were identified that were not found initially on patients, only one patient subsequently acquired the same strain. Five other patients became colonized with new MRSA strains, but these were not found in their environment beforehand. Of 52 patients colonized with MRSA, 34 had a similar strain found subsequently in their environment. CONCLUSIONS: Whereas the MRSA-colonized patient frequently contaminates his or her local environment, transmission of MRSA from the environment to the patient was not commonly identified. Studies elucidating possible routes of MRSA transmission are urgently needed to inform infection control policies.