Serial survey of methicillin-resistant Staphylococcus aureus nasal carriage among residents in a nursing home

OBJECTIVE: To study the natural course of nasal colonization by methicillin-resistant Staphylococcus aureus (MRSA) among residents in a nursing home. DESIGN: A cohort study with eight surveys of nasal cultures over 15 months. SETTING: A community nursing home in Chicago, Illinois. PARTICIPANTS: Between 117 and 129 residents of the nursing home in each survey. RESULTS: MRSA carriers were present throughout the study period. On the average, 24.4% (range: 17.1% to 34.2%) of the residents carried S aureus, and 35.3% (range: 20% to 62.5%) of the isolates were methicillin resistant at each survey. The carrier state was persistent or transient and was affected little by a roommate's carrier status. Approximately 70% to 80% of residents who were bedridden or who had decubitus ulcers or foreign bodies carried MRSA at least once during the study period. Residents' prior hospitalization was not associated with MRSA carriage. CONCLUSION: This study demonstrated that MRSA was perpetuated in the nursing home by persistently or intermittently colonizing debilitated residents who required more intensive nursing care and that the prior hospitalization of the residents was not an important cause of its perpetuation.