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Updated: Jul 19, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Epidemiology of methicillin-resistant Staphylococcus aureus colonization in a surgical intensive care unit
David K Warren1, Rebecca M Guth, Craig M Coopersmith
1Division of Infectious Diseases, Washington University School of Medicine, Barnes Jewish Hospital, Saint Louis, MO 63110, USA. dwarren@im.wustl.edu
Background:
Methicillin-resistant Staphylococcus aureus (MRSA) is a cause of healthcare-associated infections among surgical intensive care unit (ICU) patients, though transmission dynamics are unclear.
Objective:
To determine the prevalence of MRSA nasal colonization at ICU admission, to identify associated independent risk factors, to determine the value of these factors in active surveillance, and to determine the incidence of and risk factors associated with MRSA acquisition.
Design:
Prospective cohort study.
Setting:
Surgical ICU at a teaching hospital.
Patients:
All patients admitted to the surgical ICU.
Results:
Active surveillance for MRSA by nasal culture was performed at ICU admission during a 15-month period. Patients who stayed in the ICU for more than 48 hours had nasal cultures performed weekly and at discharge from the ICU, and clinical data were collected prospectively. Of 1,469 patients, 122 (8%) were colonized with MRSA at admission; 75 (61%) were identified by surveillance alone. Among 775 patients who stayed in the ICU for more than 48 hours, risk factors for MRSA colonization at admission included the following: hospital admission in the past year (1-2 admissions: adjusted odds ratio [aOR], 2.60 [95% confidence interval {CI}, 1.47-4.60]; more than 2 admissions: aOR, 3.56 [95% CI, 1.72-7.40]), a hospital stay of 5 days or more prior to ICU admission (aOR, 2.54 [95% CI, 1.49-4.32]), chronic obstructive pulmonary disease (aOR, 2.16 [95% CI, 1.17-3.96]), diabetes mellitus (aOR, 1.87 [95% CI, 1.10-3.19]), and isolation of MRSA in the past 6 months (aOR, 8.18 [95% CI, 3.38-19.79]). Sixty-nine (10%) of 670 initially MRSA-negative patients acquired MRSA in the ICU (corresponding to 10.7 cases per 1,000 ICU-days at risk). Risk factors for MRSA acquisition included tracheostomy in the ICU (aOR, 2.18 [95% CI, 1.13-4.20]); decubitus ulcer (aOR, 1.72 [95% CI, 0.97-3.06]), and receipt of enteral nutrition via nasoenteric tube (aOR, 3.73 [95% CI, 1.86-7.51]), percutaneous tube (aOR, 2.35 [95% CI, 0.74-7.49]), or both (aOR, 3.33 [95% CI, 1.13-9.77]).
Conclusions:
Active surveillance detected a sizable proportion of MRSA-colonized patients not identified by clinical culture. MRSA colonization on admission was associated with recent healthcare contact and underlying disease. Acquisition was associated with potentially modifiable processes of care.
Insights
Active surveillance identified a significant number of Methicillin-resistant Staphylococcus aureus (MRSA) carriers upon surgical intensive care unit (ICU) admission. Risk factors for MRSA colonization and acquisition were identified, highlighting opportunities for intervention.
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat, causing healthcare-associated infections in surgical intensive care unit (ICU) patients.
- Understanding MRSA transmission dynamics within the ICU is crucial for effective infection control.
Purpose of the Study:
- To determine the prevalence of MRSA nasal colonization at ICU admission.
- To identify independent risk factors for MRSA colonization and acquisition.
- To evaluate the utility of these factors in active surveillance strategies.
Main Methods:
- A prospective cohort study was conducted in a surgical ICU.
- 1,469 patients admitted to the ICU were monitored over a 15-month period.
- Nasal cultures were performed at admission, weekly for prolonged stays, and at discharge, with prospective clinical data collection.
Main Results:
- 8% of patients (122/1,469) were colonized with MRSA upon admission, with 61% detected only by active surveillance.
- Risk factors for admission colonization included prior hospital admissions, prolonged prior hospital stays, COPD, diabetes, and recent MRSA isolation.
- 10% of initially MRSA-negative patients acquired MRSA in the ICU, with risk factors including tracheostomy, decubitus ulcers, and enteral nutrition routes.
Conclusions:
- Active surveillance is effective in identifying MRSA-colonized patients missed by routine clinical cultures.
- MRSA colonization at admission is linked to prior healthcare exposure and comorbidities.
- MRSA acquisition in the ICU is associated with modifiable care processes, suggesting targets for prevention.
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