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Updated: May 26, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Changing epidemiology of methicillin-resistant Staphylococcus aureus in the Veterans Affairs Healthcare System,
1Infectious Diseases Research Program, Veterans Affairs Medical Center (151), Providence, RI 02908, USA.
Purpose:
The epidemiology of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) is changing. Temporal trends and differences between healthcare settings must be described in order to better predict future risk factors associated with this dangerous bacterial infection.
Methods:
A national MRSA-infected cohort was identified from 2002 to 2009 in the Veterans Affairs Healthcare System of the United States: hospital (HOS), long-term care (LTC), and outpatient (OPT). We analyzed within-setting time trends using generalized linear mixed models and between-setting differences with χ(2) and Wilcoxon rank-sum tests.
Results:
The incidence of S. aureus, methicillin-susceptible S. aureus (MSSA), and MRSA infections increased significantly over time in all three settings based on modeled annual percentage changes (P < 0.001). MRSA incidence rates rose by 14, 10, and 37% per year in the HOS, LTC, and OPT settings, respectively. Among 56,345 MRSA-infected patients, the comorbidity burden was highest among LTC inpatients (n = 4,427) and lowest among outpatients (n = 7,250), with an average absolute difference in specific comorbidities of +2 and -7%, respectively, compared to HOS inpatients (n = 44,668). Over time, there was a significant (P ≤ 0.02) decrease in previous inpatient admissions and surgeries (all settings); diabetes with complications and surgical site infections (HOS, OPT); and median length of stay and inpatient mortality (HOS, LTC). Alternatively, obesity, chronic renal disease, and depression were more common between 2002 and 2009 (P ≤ 0.02).
Conclusions:
Over the past 8 years, we observed significant changes in the epidemiology of MRSA infections, including decreases in traditional MRSA risk factors, improvements in clinical outcomes, and increases in other patient characteristics that may affect risk.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) infections are rising across all healthcare settings, with significant increases in outpatient MRSA incidence. Traditional risk factors decreased, but new patient characteristics emerged, impacting infection risk.
Area of Science:
- Infectious Diseases
- Epidemiology
- Healthcare-Associated Infections
Background:
- The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) is dynamic and varies across healthcare settings.
- Understanding temporal trends and setting-specific differences is crucial for predicting future MRSA risk factors.
Purpose of the Study:
- To analyze temporal trends and differences in MRSA infection epidemiology within and between hospital, long-term care, and outpatient settings.
- To identify changing risk factors and patient characteristics associated with MRSA infections.
Main Methods:
- A national cohort of MRSA-infected patients in the Veterans Affairs Healthcare System from 2002-2009 was analyzed.
- Generalized linear mixed models and statistical tests (χ(2), Wilcoxon rank-sum) were used to assess time trends and setting differences.
Main Results:
- MRSA incidence significantly increased annually in hospital (14%), long-term care (10%), and outpatient (37%) settings.
- Comorbidity burden was highest in long-term care. Traditional risk factors like prior admissions and surgeries decreased, while obesity and chronic renal disease increased.
- Clinical outcomes improved, with decreased length of stay and inpatient mortality in some settings.
Conclusions:
- Significant epidemiological shifts in MRSA infections occurred between 2002-2009.
- Decreases in traditional MRSA risk factors and improvements in outcomes were observed.
- Emerging patient characteristics may influence future MRSA risk and management strategies.
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