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Updated: Apr 16, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Multicenter Observational Study on Factors and Outcomes Associated with Various Methicillin-Resistant Staphylococcus
Marianne S Muhlebach1, Sonya L Heltshe2,3, Elena B Popowitch4
11 Department of Pediatrics, Division of Pediatric Pulmonology, and.
Rationale:
Methicillin-resistant Staphylococcus aureus (MRSA) prevalence continues to increase in patients with cystic fibrosis (CF) in the United States, reaching 26.5% in 2012. Approximately 30% of strains are SCCmec (staphylococcal cassette chromosome mec) IV type, frequently USA300, which in the general population have different genotypic and phenotypic features than SCCmec II type.
Objectives:
We hypothesized that risk factors for acquisition and outcomes in patients with CF differed for "health care-associated" (SCCmec II) versus "community-associated" (SCCmec IV) MRSA strains.
Methods:
To determine the role of SCCmec type and Panton-Valentine leukocidin (PVL), MRSA isolates from patients not more than 18 years old at seven CF centers were typed and the association of potential risk factors and subsequent clinical course was assessed, using data provided by the CF Patient Registry.
Measurements And Main Results:
Participants with chronic MRSA (295) had typeable isolates and clinical data; 205 (69.5%) had SCCmec II PVL(-), 39 (13.2%) had SCCmec IV PVL(-), and 51 (17.3%) had SCCmec IV PVL(+) strains. SCCmec IV, compared with SCCmec II, increased during the study period, 1996-2010 (P = 0.03). SCCmec II was associated with Pseudomonas aeruginosa-positive cultures and three or more clinic visits in the 6 months preceding the first positive MRSA culture (adjusted odds ratio, 2.05; 95% confidence interval, 1.13-3.74; P = 0.019). Lung function and anthropometrics remained unchanged in the 6 months after initial MRSA detection compared with the 6 months prior. Although CF care increased for participants in both groups in the 6 months after MRSA detection, inhaled antibiotics were prescribed more frequently in those with SCCmec II strains and increased hospitalizations occurred in those with SCCmec IV PVL(-) strains compared with those with PVL(+) strains (adjusted difference, 34.10%; 95% confidence interval, 7.58-60.61; P = 0.012). Participants in both groups had an increase in CF care in the 2 years after MRSA detection compared with the 2 years prior.
Conclusions:
Increased exposure to CF clinics and P. aeruginosa may constitute risk factors for acquisition of SCCmec II MRSA strains. Clinical interventions increased 6 months and 2 years after initial MRSA detection regardless of SCCmec type.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) strains in cystic fibrosis (CF) patients vary by type, with SCCmec II linked to healthcare exposure and SCCmec IV to community settings. Clinical care increased post-detection regardless of MRSA strain type.
Area of Science:
- Infectious Diseases
- Microbiology
- Pulmonology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) prevalence is rising in cystic fibrosis (CF) patients.
- Approximately 30% of MRSA strains in CF patients are SCCmec IV type (e.g., USA300), differing from SCCmec II strains.
Purpose of the Study:
- To investigate if risk factors for MRSA acquisition and subsequent outcomes differ between healthcare-associated (SCCmec II) and community-associated (SCCmec IV) MRSA strains in CF patients.
- To determine the role of SCCmec type and Panton-Valentine leukocidin (PVL) in MRSA infections within this population.
Main Methods:
- MRSA isolates from pediatric CF patients at seven centers were typed for SCCmec type and PVL.
- Data from the CF Patient Registry were used to assess risk factors and clinical outcomes.
- Analysis compared patients with SCCmec II, SCCmec IV PVL(-), and SCCmec IV PVL(+) strains.
Main Results:
- SCCmec IV strains increased in prevalence from 1996-2010.
- SCCmec II strains were associated with Pseudomonas aeruginosa-positive cultures and increased clinic visits.
- Hospitalizations increased in SCCmec IV PVL(-) strains compared to PVL(+) strains, while lung function and anthropometrics remained stable post-detection.
Conclusions:
- Healthcare exposure and P. aeruginosa may be risk factors for SCCmec II MRSA acquisition in CF patients.
- Clinical interventions and CF care increased after MRSA detection, irrespective of SCCmec type.
- Understanding strain-specific differences is crucial for managing MRSA in CF.
