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Updated: Jun 24, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Characterization of methicillin-resistant Staphylococcus aureus isolates collected in 2005 and 2006 from patients
Brandi Limbago1, Gregory E Fosheim, Valerie Schoonover
1Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. BBL7@cdc.gov
Abstract:
This study characterizes 1,984 methicillin-resistant Staphylococcus aureus (MRSA) isolates collected in 2005 and 2006 from normally sterile sites in patients with invasive MRSA infection. These isolates represent a convenience sample of all invasive MRSA cases reported as part of the Active Bacterial Core surveillance system in eight states in the United States. The majority of isolates were from blood (83.8%), joints (4.1%), and bone (4.2%). Isolates were characterized by pulsed-field gel electrophoresis (PFGE); SCCmec typing; susceptibility to 15 antimicrobial agents; and PCR analysis of staphylococcal enterotoxin A (SEA) to SEH, toxic shock syndrome toxin 1, and Panton-Valentine leukocidin. Thirteen established PFGE types were recognized among these isolates, although USA100 and USA300 predominated, accounting for 53.2% and 31.4% of the isolates, respectively. As expected, isolates from hospital onset cases were predominantly USA100, whereas those from community-associated cases were predominantly USA300. USA100 isolates were diverse (Simpson's discriminatory index [DI] = 0.924); generally positive only for enterotoxin D (74.5%); and resistant to clindamycin (98.6%), erythromycin (99.0%), and levofloxacin (99.6%), in addition to beta-lactam agents. USA300 isolates were less diverse (DI = 0.566), positive for Panton-Valentine leukocidin (96.3%), and resistant to erythromycin (94.1%) and, less commonly, levofloxacin (54.6%), in addition to beta-lactam agents. This collection provides a reference collection of MRSA isolates associated with invasive disease, collected in 2005 and 2006 in the United States, for future comparison and ongoing studies.
Insights
This study analyzed 1,984 invasive methicillin-resistant Staphylococcus aureus (MRSA) isolates from 2005-2006. USA100 and USA300 strains predominated, with distinct characteristics and antimicrobial resistance patterns observed between hospital-onset and community-associated infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Epidemiology
Background:
- Invasive methicillin-resistant Staphylococcus aureus (MRSA) infections pose a significant public health challenge.
- Understanding the molecular epidemiology and antimicrobial resistance profiles of circulating MRSA strains is crucial for effective treatment and control.
Purpose of the Study:
- To characterize a large collection of invasive MRSA isolates from the United States collected in 2005 and 2006.
- To identify predominant MRSA pulsed-field gel electrophoresis (PFGE) types and analyze their genotypic and antimicrobial resistance characteristics.
- To compare MRSA isolates from hospital-onset versus community-associated invasive infections.
Main Methods:
- Characterization of 1,984 invasive MRSA isolates using pulsed-field gel electrophoresis (PFGE) and SCCmec typing.
- Antimicrobial susceptibility testing against 15 agents.
- Polymerase chain reaction (PCR) analysis for staphylococcal enterotoxin genes and Panton-Valentine leukocidin.
Main Results:
- USA100 (53.2%) and USA300 (31.4%) were the predominant PFGE types.
- Hospital-onset cases were mainly USA100, while community-associated cases were predominantly USA300.
- USA100 isolates showed high resistance to clindamycin, erythromycin, and levofloxacin; USA300 isolates were positive for Panton-Valentine leukocidin and showed high erythromycin resistance.
Conclusions:
- The study provides a valuable reference collection of invasive MRSA isolates from a specific period in the US.
- Distinct molecular and resistance profiles of USA100 and USA300 underscore their differing epidemiological roles.
- Ongoing surveillance and characterization of MRSA are essential for tracking evolving resistance and virulence traits.
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