Related Experiment Video
Updated: Jun 13, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Staphylococcus aureus nasal colonization and subsequent infection in intensive care unit patients: does methicillin
Hitoshi Honda1, Melissa J Krauss, Craig M Coopersmith
1Division of Infectious Diseases, Washington University School of Medicine, St Louis, Missouri 63110, USA. hhonda@im.wustl.edu
Background:
Staphylococcus aureus is an important cause of infection in intensive care unit (ICU) patients. Colonization with methicillin-resistant S. aureus (MRSA) is a risk factor for subsequent S. aureus infection. However, MRSA-colonized patients may have more comorbidities than methicillin-susceptible S. aureus (MSSA)-colonized or noncolonized patients and therefore may be more susceptible to infection on that basis.
Objective:
To determine whether MRSA-colonized patients who are admitted to medical and surgical ICUs are more likely to develop any S. aureus infection in the ICU, compared with patients colonized with MSSA or not colonized with S. aureus, independent of predisposing patient risk factors.
Design:
Prospective cohort study.
Setting:
A 24-bed surgical ICU and a 19-bed medical ICU of a 1,252-bed, academic hospital.
Patients:
A total of 9,523 patients for whom nasal swab samples were cultured for S. aureus at ICU admission during the period from December 2002 through August 2007.
Methods:
Patients in the ICU for more than 48 hours were examined for an ICU-acquired S. aureus infection, defined as development of S. aureus infection more than 48 hours after ICU admission.
Results:
S. aureus colonization was present at admission for 1,433 (27.8%) of 5,161 patients (674 [47.0%] with MRSA and 759 [53.0%] with MSSA). An ICU-acquired S. aureus infection developed in 113 (2.19%) patients, of whom 75 (66.4%) had an infection due to MRSA. Risk factors associated with an ICU-acquired S. aureus infection included MRSA colonization at admission (adjusted hazard ratio, 4.70 [95% confidence interval, 3.07-7.21]) and MSSA colonization at admission (adjusted hazard ratio, 2.47 [95% confidence interval, 1.52-4.01]).
Conclusion:
ICU patients colonized with S. aureus were at greater risk of developing a S. aureus infection in the ICU. Even after adjusting for patient-specific risk factors, MRSA-colonized patients were more likely to develop S. aureus infection, compared with MSSA-colonized or noncolonized patients.
Insights
Patients colonized with Staphylococcus aureus (S. aureus) in the ICU face a higher risk of developing S. aureus infections. Methicillin-resistant S. aureus (MRSA) colonization significantly increases this risk, even after accounting for other patient factors.
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Microbiology
Background:
- Staphylococcus aureus is a frequent cause of infection in intensive care unit (ICU) patients.
- Colonization with methicillin-resistant S. aureus (MRSA) is a known risk factor for subsequent S. aureus infection.
- MRSA-colonized patients may have more comorbidities, potentially increasing susceptibility to infection.
Purpose of the Study:
- To investigate if MRSA-colonized ICU patients are more prone to developing S. aureus infections compared to MSSA-colonized or non-colonized patients.
- To determine this risk independently of other patient risk factors.
Main Methods:
- Prospective cohort study conducted in medical and surgical ICUs.
- Nasal swab cultures for S. aureus performed on 9,523 patients at ICU admission.
- ICU-acquired S. aureus infection defined as infection developing >48 hours post-admission.
Main Results:
- S. aureus colonization was identified in 27.8% of patients (MRSA: 47.0%, MSSA: 53.0%).
- ICU-acquired S. aureus infection occurred in 2.19% of patients, with MRSA being the causative agent in 66.4% of these cases.
- MRSA colonization at admission (aHR, 4.70) and MSSA colonization (aHR, 2.47) were significant risk factors for ICU-acquired S. aureus infection.
Conclusions:
- S. aureus colonization at ICU admission increases the risk of developing S. aureus infection during the ICU stay.
- MRSA-colonized patients exhibit a significantly higher likelihood of developing S. aureus infection compared to MSSA-colonized or non-colonized patients, even after adjusting for patient-specific risk factors.
Related Concept Videos
01:25Clinical Significance of Antibiotic Resistance
01:25Mechanism of Antibiotic Resistance in MRSA
01:29Staphylococcal Skin Infections
01:29Microbiota of the Respiratory Tract
01:31Defense Against Bacterial Pathogens
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...
01:30Development of Antibiotic Resistance