Abstract

Background

Methicillin-resistant Staphylococcus aureus (MRSA) infects ∼25% of patients with cystic fibrosis (CF) in the United States. We hypothesized that health-related outcomes differed between healthcare-associated (staphylococcal cassette chromosome mec [SCC mec ] II) vs community-associated (SCC mec IV) MRSA strains in patients chronically infected with CF.

Methods

At 7 CF centers, MRSA isolates were prospectively obtained from patients ≤18 years old with 2 or more positive MRSA cultures within 1 year. Isolates were classified by SCC mec type and Panton-Valentine-leukocidin (PVL) status at a core laboratory, and sites remained blinded to SCC mec type and PVL results. Prospective clinical data including antibiotic use, respiratory symptoms, and pulmonary exacerbations were obtained.

Results

Among the 295 cohort participants with typeable MRSA isolates, 69.5% had SCC mec II PVL(−), 13.2% had SCC mec IV PVL(−), and 17.3% had SCC mec IV PVL(+) strains. During follow-up of 287 patients with prospective data after enrollment, the risk for pulmonary exacerbations was significantly higher among participants with SCC mec II than SCC mec IV strains (risk ratio [RR] = 1.13; P = .03) and higher in those with SCC mec IV PVL(−) than SCC mec IV PVL(+) strains (RR = 1.62; P < .0001). Neither decline in lung function nor changes in nutritional outcomes differed by SCC mec type or PVL status during the study period.

Conclusions

Participants harboring chronic SCC mec II MRSA received more antibiotics and may have more lung disease than those with SCC mec IV; PVL(+) isolates were not associated with more advanced disease.

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