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MRSA nasal carriage patterns and the subsequent risk of conversion between patterns, infection, and death
Kalpana Gupta1, Richard A Martinello, Melissa Young
1The National Center for Occupational Health and Infection Control COHIC, Office of Public Health, Department of Veterans Affairs, Gainesville, Florida, United States of America. Kalpana.gupta@va.gov
Background:
Patterns of methicillin-resistant S. aureus (MRSA) nasal carriage over time and across the continuum of care settings are poorly characterized. Knowledge of prevalence rates and outcomes associated with MRSA nasal carriage patterns could help direct infection prevention strategies. The VA integrated health-care system and active surveillance program provides an opportunity to delineate nasal carriage patterns and associated outcomes of death, infection, and conversion in carriage.
Methods/Findings:
We conducted a retrospective cohort study including all patients admitted to 5 acute care VA hospitals between 2008-2010 who had nasal MRSA PCR testing within 48 hours of admission and repeat testing within 30 days. The PCR results were used to define a baseline nasal carriage pattern of never, intermittently, or always colonized at 30 days from admission. Follow-up was up to two years and included acute, long-term, and outpatient care visits. Among 18,038 patients, 91.1%, 4.4%, and 4.6% were never, intermittently, or always colonized at the 30-day baseline. Compared to non-colonized patients, those who were persistently colonized had an increased risk of death (HR 2.58; 95% CI 2.18;3.05) and MRSA infection (HR 10.89; 95% CI 8.6;13.7). Being in the non-colonized group at 30 days had a predictive value of 87% for being non-colonized at 1 year. Conversion to MRSA colonized at 6 months occurred in 11.8% of initially non-colonized patients. Age >70 years, long-term care, antibiotic exposure, and diabetes identified >95% of converters.
Conclusions:
The vast majority of patients are not nasally colonized with MRSA at 30 days from acute hospital admission. Conversion from non-carriage is infrequent and can be risk-stratified. A positive carriage pattern is strongly associated with infection and death. Active surveillance programs in the year following carriage pattern designation could be tailored to focus on non-colonized patients who are at high risk for conversion, reducing universal screening burden.
Insights
Persistent methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage significantly increases the risk of death and MRSA infection. Active surveillance can be tailored to high-risk patients, reducing screening burdens.
Area of Science:
- Infectious Diseases
- Epidemiology
- Healthcare Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage patterns are not well understood across care settings.
- Understanding prevalence and outcomes of MRSA carriage can inform infection prevention.
- The VA healthcare system offers a unique setting to study MRSA carriage patterns.
Purpose of the Study:
- To characterize MRSA nasal carriage patterns over time in a large patient cohort.
- To determine the outcomes associated with different MRSA carriage patterns.
- To identify risk factors for conversion to MRSA carriage.
Main Methods:
- Retrospective cohort study of 18,038 patients admitted to VA hospitals (2008-2010).
- Nasal MRSA PCR testing within 48 hours of admission and repeat testing within 30 days.
- Two-year follow-up including acute, long-term, and outpatient care visits.
Main Results:
- 91.1% of patients were never colonized, 4.4% intermittently, and 4.6% always colonized at 30 days.
- Persistent MRSA colonization was associated with increased risk of death (HR 2.58) and MRSA infection (HR 10.89).
- 11.8% of non-colonized patients converted to colonization within 6 months; risk factors included age >70, long-term care, antibiotic exposure, and diabetes.
Conclusions:
- Most patients are not MRSA colonized at 30 days post-admission.
- Conversion to MRSA carriage is infrequent and can be predicted by specific risk factors.
- Targeted surveillance for high-risk converters can optimize infection prevention efforts.
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