Methicillin-resistant Staphylococcus aureus nasal colonization is a poor predictor of intensive care unit-acquired methicillin-resistant Staphylococcus aureus infections requiring antibiotic treatment
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Kiran V Sarikonda1, Scott T Micek, Joshua A Doherty
1Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, MO, USA.
Objective:
To test whether intensive care unit (ICU) nasal screening for methicillin-resistant Staphylococcus aureus (MRSA) predicts the presence or absence of MRSA infections requiring antimicrobial treatment.
Design:
A prospective cohort study.
Setting:
Medical ICU at Barnes-Jewish Hospital, a 1252-bed urban teaching hospital.
Patients:
Seven hundred forty-nine consecutive patients admitted to the medical ICU over a 7-mo period (November 2007 through June 2008).
Interventions:
Nasal swabs were obtained at ICU admission and weekly thereafter for MRSA detection by using polymerase chain reaction. All subjects were followed for the development of MRSA infection during their ICU stay.
Measurements And Main Results:
One hundred sixty-four (21.9%) patients had positive nasal colonization with MRSA at the time of ICU admission. The predictive accuracy of MRSA nasal colonization for ICU-acquired MRSA infections, either lower respiratory tract infection or bloodstream infection, was poor (lower respiratory tract infection: sensitivity, 24.2%; specificity, 78.5%; positive predictive value, 17.7%; and negative predictive value, 84.4%; and bloodstream infection: sensitivity, 23.1%; specificity, 78.2%; positive predictive value, 11.0%; and negative predictive value, 89.7%). Addition of nasal-colonization results obtained during the ICU stay did not appreciably change the predictive accuracy of this test for identification of subsequent lower respiratory tract infections and bloodstream infections attributed to MRSA requiring antimicrobial treatment.
Conclusions:
In this analysis, nasal colonization with MRSA was found to be a poor predictor for the subsequent occurrence of MRSA lower respiratory tract infections and MRSA bloodstream infections requiring antimicrobial treatment. Clinicians should be cautious in using the results of nasal-colonization testing to determine the need for MRSA treatment among patients with ICU-acquired infections.
Insights
Nasal screening for methicillin-resistant Staphylococcus aureus (MRSA) poorly predicts MRSA infections in the ICU. Clinicians should not rely solely on nasal colonization tests to guide MRSA treatment decisions for ICU patients.
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Clinical Microbiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of healthcare-associated infections.
- Nasal colonization is a known risk factor for MRSA infections, but its predictive value in the intensive care unit (ICU) setting requires further investigation.
Purpose of the Study:
- To evaluate the predictive accuracy of ICU nasal screening for methicillin-resistant Staphylococcus aureus (MRSA) in identifying subsequent MRSA infections requiring antimicrobial treatment.
Main Methods:
- A prospective cohort study was conducted involving 749 consecutive patients admitted to a medical ICU.
- Nasal swabs were collected at ICU admission and weekly for MRSA detection using polymerase chain reaction.
- Patients were monitored throughout their ICU stay for the development of MRSA infections, including lower respiratory tract and bloodstream infections.
Main Results:
- Of the 749 patients, 21.9% had positive MRSA nasal colonization upon ICU admission.
- MRSA nasal colonization demonstrated poor predictive accuracy for both lower respiratory tract infections (sensitivity 24.2%, PPV 17.7%) and bloodstream infections (sensitivity 23.1%, PPV 11.0%).
- Continued nasal screening during the ICU stay did not significantly improve the prediction of subsequent MRSA infections.
Conclusions:
- Nasal colonization with MRSA is an unreliable predictor of subsequent MRSA lower respiratory tract and bloodstream infections requiring antimicrobial treatment in the ICU.
- Clinicians should exercise caution when using nasal colonization test results to guide MRSA treatment decisions in ICU-acquired infections.
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