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

Abstract

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 FEV(1) decline in CF is unknown. To determine the association between MRSA respiratory infection and FEV(1) decline in children and adults with CF. 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 FEV(1) 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. 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 (> or =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 FEV(1) decline in individuals aged 8-21 years with persistent MRSA was more rapid in both statistical models. Their average FEV(1) 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 FEV(1) decline in adults was not clinically significant. 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.