Robert R. Muder, MD; Carole Brennen, RN, MSN; Marilyn M. Wagener, MPH; Richard M. Vickers, BS; John D. Rihs, BS; Gary A. Hancock, BS; Ying C. Yee, MS; J. Michael Miller, PhD; Victor L. Yu, MD
Objective: To determine the natural history of colonization by methicillin-resistant Staphylococcus aureus (MRSA) among patients in a long-term care facility. We specifically sought to determine if MRSA colonization was predictive of subsequent infection.
Design: Cohort study.
Setting: Long-term Veterans Affairs Medical Center.
Patients: A total of 197 patients residing on two units were followed with regular surveillance cultures of the anterior nares.
Main Outcome Measurement: The development of staphylococcal infection.
Results: Thirty-two patients were persistent carriers of MRSA and 44 were persistent carriers of methicillin-susceptible strains (MSSA). Twenty-five percent of MRSA carriers had an episode of staphylococcal infection compared with 4% of MSSA carriers and 4.5% of non-carriers (P < 0.01; relative risk 3.8; 95% CI, 2.0 to 6.4). The rate of development of infection among MRSA carriers was 15% for every 100 days of carriage. Using logistic regression analysis, persistent MRSA carriage was the most significant predictor of infection (P < 0.001; odds ratio, 3.7). Seventy-three percent of all MRSA infections occurred among MRSA carriers. Isolates of MRSA from 7 patients were typed. Colonizing and infecting strains had the same phage type in all 7 patients and the same pattern of plasmid EcoRI restriction endonuclease fragments in 5 patients.
Conclusions: Colonization of the anterior nares by MRSA predicts the development of staphylococcal infection in long-term care patients; most infections arise from endogenously carried strains. Colonization by MRSA indicates a significantly greater risk for infection than does colonization by MSSA. The results offer a theoretic rationale for reduction in MRSA infections by interventions aimed at eliminating the carrier state.
Robert R. Muder, Carole Brennen, Marilyn M. Wagener, Richard M. Vickers, John D. Rihs, Gary A. Hancock, et al. Methicillin-Resistant Staphylococcal Colonization and Infection in a Long-Term Care Facility. Ann Intern Med. 1991;114:107–112. doi: 10.7326/0003-4819-114-2-1-107
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Published: Ann Intern Med. 1991;114(2):107-112.
Geriatric Medicine, Infectious Disease.
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