Infections caused by Staphylococcus aureus in a Veterans' Affairs nursing home care unit: a 5-year experience

To describe the frequency and patterns of infection caused by methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S aureus (MRSA) infections in a single nursing home population and to determine the effect of MRSA's entry into the facility on subsequent experience with both MSSA and MRSA infections.

Observational and descriptive. Surveillance data on nursing home-acquired infections were reviewed to identify all patients with MSSA and MRSA infections occurring during the 5-year period from 1987 to 1991. The medical records of these patients were reviewed retrospectively to collect additional information about the patients and their infections.

A 120-bed Veterans' Affairs nursing home care unit (NHCU) whose residents predominantly were elderly men with severe underlying diseases and functional impairments.

During the 5-year study period, 40 MSSA and 28 MRSA infections were acquired by NHCU residents. Twelve to 19 S aureus infections occurred each year. S aureus accounted for 13% to 17% of all NHCU-acquired infections during the years of study, occurring with a frequency of 0.29 to 0.47 infections per 1,000 resident-care days. MRSA infections, first detected in 1988, accounted for an increasing percentage of S aureus infections in subsequent years, but this increase had little effect on the facility's overall infection rates, the composite S aureus infection rates, or the types of infections observed. MSSA and MRSA infections acquired in the NHCU were comparable. Both affected patients with severe underlying diseases and functional impairments. Pneumonia, urinary tract infections, skin and soft tissue infections, and conjunctivitis were the types of infections observed most frequently, accounting for 28%, 25%, 22%, and 15% of all S aureus infections, respectively. Four bacteremic infections occurred in the MSSA group, and five in the MRSA group (P = .47). Four of the MSSA and three of the MRSA infections resulted in death (P = 1.0). Nine of the MSSA and 12 of the MRSA infections resulted in the patient's transfer to the associated acute care hospital for additional care (P = .13).

In the NHCU setting, MSSA and MRSA infections were similar in terms of the types of residents affected, the sites involved, and the frequency of adverse outcomes. The entry of MRSA into the facility appeared to have no effect on the subsequent experience with NHCU-acquired infections caused by S aureus.