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.
DESIGN: 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.
SETTING AND PATIENTS: 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).
CONCLUSIONS: 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.