Methicillin-resistant Staphylococcus aureus in a nursing home and affiliated hospital: a four-year perspective.

OBJECTIVES: To determine the effect of a methicillin-resistant Staphylococcus aureus (MRSA) outbreak in a nursing home on the subsequent MRSA caseload in a closely affiliated hospital.

DESIGN: Observational and descriptive; routine and special MRSA surveillance data for nursing home and hospital were reviewed for a four-year period (1988 to 1991) as were records regarding patient transfers from nursing home to hospital.

SETTING: The 120-bed nursing home care unit (NHCU) and the geographically separate 434-bed acute care facility (hospital) of the Portland Veterans' Affairs Medical Center (PVAMC).

PATIENTS: Veterans hospitalized in the acute care division of NHCU.

RESULTS: Following the introduction of MRSA into the NHCU in December 1987, it quickly disseminated. Two to 32 newly colonized or infected patients were recognized in each quarter of the study period. Facility-wide prevalence surveys on two occasions disclosed MRSA colonization rates of 34% and 10%. During the study period, 15 to 54 (mean: 37.6) patients were transferred each quarter from the NHCU to the hospital of the PVAMC. The number of MRSA cases transferred ranged from 0 to 16 per quarter (mean: 5.4). During the same period, the total number of MRSA cases in the hospital increased, rising from 7 cases in 1987 to 16 in 1988, 48 in 1989, 34 in 1990, and 35 in 1991. The percentage of hospital MRSA cases accounted for by NHCU transfers was 0% in 1988, 38% in 1989, 12% in 1990, and 11% in 1991.

CONCLUSIONS: Despite the steady flow of patients between the NHCU and the hospital, the MRSA outbreak in the NHCU was associated with only a modest increase in the MRSA caseload at the affiliated hospital.