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Updated: Sep 29, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a Veterans Administration Medical Center
Loreen A Herwaldt1, Jean M Pottinger, Stacy Coffman
1The University of Iowa Hospitals and Clinics, Iowa City 52242-081, USA.
Objectives:
To determine whether patients who were colonized or infected with methicillin-resistant Staphylococcus aureus (MRSA) persistently carried the same strain and to identify the extent of strain variation within a population of patients.
Design:
Molecular typing by pulsed-field gel electrophoresis (PFGE) of stored MRSA isolates.
Setting:
A Veterans Administration Medical Center with 288 hospital, 45 intermediate-care, and 75 extended-care beds. ISOILATES: Between January 1991 and March 1993, 91 patients had MRSA identified in routine cultures. One hundred isolates from 57 patients (63%) were available for typing.
Results:
Before 1988, only occasional MRSA isolates were identified. By 1993, 50% of S. aureus isolates from unique patients were resistant to methicillin. PFGE identified 7 MRSA strains, 3 of which were identified in specimens from 1 patient each. The most common strains were SD4 (20 patients), SD1 (12 patients), SD2 (12 patients), and SD5a (5 patients). Twenty patients had 2 or more isolates obtained at least 1 week apart (mean, 30.7 weeks; range, 1 to 102 weeks). Of these patients, 12 were colonized or infected with only one strain (mean time observed, 25.1 weeks; range, 1 to 82 weeks). Eight patients had at least 2 different strains (mean time observed, 39 weeks; range, 2 to 102 weeks).
Conclusion:
Numerous MRSA strains circulated in this endemic setting, 40% of patients observed over time were colonized or infected with more than one strain. Molecular typing was an essential tool for evaluating the epidemiology of MRSA in this setting.
Insights
Patients frequently carried multiple strains of methicillin-resistant Staphylococcus aureus (MRSA), indicating significant strain variation. Molecular typing confirmed diverse MRSA strains circulating within the healthcare setting over time.
Area of Science:
- Infectious Diseases
- Microbiology
- Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant healthcare challenge.
- Understanding MRSA strain dynamics is crucial for infection control.
Purpose of the Study:
- To investigate persistent carriage of specific MRSA strains in patients.
- To determine the extent of MRSA strain variation within a patient population.
Main Methods:
- Molecular typing using pulsed-field gel electrophoresis (PFGE) was performed on MRSA isolates.
- Analysis of isolates from 57 patients collected between January 1991 and March 1993.
Main Results:
- Seven distinct MRSA strains were identified among the patient population.
- Twenty patients provided isolates over extended periods; 8 (40%) harbored multiple MRSA strains.
- Specific strains like SD4, SD1, and SD2 were most prevalent.
Conclusions:
- A diverse array of MRSA strains circulated within the studied healthcare setting.
- A significant proportion of patients (40%) were found to carry more than one MRSA strain over time.
- PFGE is an essential tool for elucidating MRSA epidemiology in endemic environments.
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