Risk factors for persistent methicillin-resistant Staphylococcus aureus infection in cystic fibrosis.

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as an important pathogen in cystic fibrosis (CF). Over 25% of individuals in the United States with CF are found to have MRSA in respiratory culture specimens, and persistent MRSA infection has been associated with more rapid decline in lung function and increased mortality. The objective of this study was to investigate clinical and demographic characteristics that are associated with the development of persistent MRSA infection in a CF population.

METHODS

This was a retrospective cohort study of individuals followed from 2002 to 2012 in the Cystic Fibrosis Foundation Patient Registry. A time-to-event analysis for the development of persistent MRSA infection was performed, and multivariable Cox proportional hazards models were constructed to identify risk factors for infection.

RESULTS

The study cohort included 19,434 individuals, of which 5844 would develop persistent MRSA infection. In the adjusted model, pancreatic insufficiency (HR: 1.49; 95% CI: 1.29-1.72), CF related diabetes (HR: 1.13; 95% CI: 1.05-1.20), co-infection with P. aeruginosa (HR: 1.21; 95% CI: 1.13-1.28), and number of hospitalizations/year (HR: 1.09; 95% CI: 1.06-1.12) were all associated with increased risk, whereas higher socio-economic status (HR: 0.87; 95% CI: 0.82-0.93) was associated with a lower risk. Receiving care at a CF center with increased MRSA prevalence was associated with increased risk of MRSA infection: highest quartile (HR: 2.33; 95% CI: 2.13-2.56).

CONCLUSIONS

No easily modifiable risk factors for persistent MRSA were identified in this study. However, several risk factors for patients at higher risk for persistent MRSA infection were identified, for example centers with a high baseline MRSA prevalence, and may be useful in designing center-specific MRSA infection prevention and control strategies and/or eradication protocols. Additional studies are needed in order to evaluate if attention to these risk factors can improve clinical outcomes.