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Persistent Methicillin-resistant Staphylococcus aureus and Rate of FEV₁ Decline in Cystic Fibrosis

¹ Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, and ² Departments of Biostatistics and Epidemiology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland

Correspondence and requests for reprints should be addressed to Elliott C. Dasenbrook, M.D., The Johns Hopkins University School of Medicine, 1830 E. Monument Street, 5th Floor, Baltimore, MD 21205. E-mail: edasenb1{at}jhmi.edu

Rationale: The prevalence in cystic fibrosis (CF) of respiratory cultures with methicillin-resistant Staphylococcus aureus (MRSA) has dramatically increased over the last 10 years, but the effect of MRSA on FEV₁ decline in CF is unknown.

Objectives: To determine the association between MRSA respiratory infection and FEV₁ decline in children and adults with CF.

Methods: This was a 10-year cohort study using the Cystic Fibrosis Foundation patient registry from 1996–2005. We studied individuals who developed new MRSA respiratory tract infection. Repeated-measures regression was used to assess the association between MRSA and FEV₁ decline, adjusted for confounders, in individuals aged 8–21 years and adults (aged 22–45 yr). Two different statistical models were used to assess robustness of results.

Measurements and Main Results: The study cohort included 17,357 patients with an average follow-up of 5.3 years. During the study period, 1,732 individuals developed new persistent MRSA infection (3 MRSA cultures; average, 6.8 positive cultures) and were subsequently followed for an average of 3.5 years. Even after adjustment for confounders, rate of FEV₁ decline in individuals aged 8–21 years with persistent MRSA was more rapid in both statistical models. Their average FEV₁ decline of 2.06% predicted/year was 43% more rapid than the 1.44% predicted/year in those without MRSA (difference, –0.62% predicted/yr; 95% confidence interval, –0.70 to –0.54; P < 0.001). Effect of MRSA on FEV₁ decline in adults was not clinically significant.

Conclusions: Persistent infection with MRSA in individuals with CF between the ages of 8 and 21 years is associated with a more rapid rate of decline in lung function.

Key Words: cystic fibrosis • methicillin-resistant Staphylococcus aureus • longitudinal studies • pulmonary function test • epidemiology

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in individuals with cystic fibrosis has increased in recent years. Whether MRSA contributes to a more rapid rate of lung function decline is unknown. What This Study Adds to the Field This study suggests that, even after controlling for severity of illness, persistent infection with MRSA in individuals with cystic fibrosis aged 8–21 is associated with a more rapid decline of lung function.

 

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