A longitudinal analysis of chronic MRSA and Pseudomonas aeruginosa co-infection in cystic fibrosis: A single-center study

Background: Few studies have examined the association between chronic methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PA) co-infection and health outcomes despite evidence that these pathogens alone contribute to higher morbidity and mortality in cystic fibrosis (CF). This study examines outcomes among CF patients with chronic MRSA and PA co-infection compared with patients with either or neither of these organisms. Methods: CF patients attending the care center in Atlanta, GA from 2007-2013 comprised the study cohort. Chronic co-infection was defined as >50% PA + cultures and >50% MRSA + cultures and modeled as time-varying. The rate of decline in lung function (FEV1) and the rate of IV treatments were the main outcomes. Results: Among all patients (N = 354), chronic co-infection was associated with a significantly more rapid rate of FEV1 decline compared with patients with chronic PA alone [adjusted difference: -0.60% predicted/year (-1.13, -0.08)] and chronic MRSA alone [adjusted difference: -0.89% predicted/year (-1.56, -0.22)]. Rate of IV treatments was significantly higher among patients with chronic co-infection compared with patients with chronic PA alone [adjusted IRR: 1.24 (1.01, 1.52)] and chronic MRSA alone [adjusted IRR: 1.34 (1.03, 1.74)]. Conclusions: Data from the Atlanta Care Center suggest that chronic MRSA and PA co-infection may be associated with increased rate of lung function decline and rate of intravenous antibiotics compared with patients with either pathogen alone. (C) 2015 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.