Chronic MRSA and P. aeruginosa Co-infection and Rate of Lung Function Decline Among Patients with Cystic Fibrosis Open Access

Maliniak, Maret Lee (2014)

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Background: Chronic Pseudomonas aeruginosa infection is a well-known risk factor for increased lung function decline among patients with cystic fibrosis (CF). More recently, studies have found that chronic MRSA infection may also contribute to lungfunction decline. However, the association between chronic MRSA and P. aeruginosa co-infection and rate of lung function decline has not been widely studied.

Objective: This study aims to characterize CF patients with chronic MRSA and P. aeruginosa co-infection and examine whether these patients have a higher rate of lung function decline, measured by forced expiratory volume in the first second (FEV1, given as % predicted) per year, compared to patients with other levels of infection.

Population: Cystic fibrosis patients (≥6 years old) attending a CF center in Atlanta, GA and included in the patient registry between 2007 and 2013 comprised the study cohort.

Study Design: Repeated measures mixed effects modeling was used to compare the rates of FEV1 decline (% predicted/year) between patients chronically co-infected with MRSA and P. aeruginosa to patients with chronic P. aeruginosa alone, chronic MRSA alone, intermittent MRSA or P. aeruginosa, and no colonization of P. aeruginosa or MRSA, adjusting for known covariates.

Results: Patients with chronic co-infection were found to have a baseline FEV1 of 62.9% predicted (standard deviation: 25.8) and a significantly more rapid rate of decline in FEV1 % predicted compared to patients without MRSA or P. aeruginosa adjusting for confounders and using all values of FEV1 recorded during follow-up (mean rate: -1.06 FEV1 % predicted per year; 95% CI: -2.08, -0.05). However, the rate of FEV1 decline was not significantly greater than that of patients with chronic P. aeruginosa, chronic MRSA alone, or intermittent infection, suggesting that chronic co-infection may not increase lung function decline beyond that of other levels of infection.

Conclusions: Chronic co-infection of MRSA and P. aeruginosa is associated with lower baseline lung function and continued decline in FEV1 % predicted; however, the rate of decline in FEV1 % predicted may not be greater than that of other common levels of infection. Future studies should investigate this association in the broader CF population.

Table of Contents

Table of Contents

1. Background/Literature Review...1

1.1. Cystic fibrosis: Background and Epidemiology...1
1.2. CF Respiratory Pathogens...6
1.3. Pseudomonas aeruginosa...8
1.4. Methicillin-resistant Staphylococcus aureus (MRSA)...13
1.5. Co-infection of MRSA and Pseudomonas aeruginosa...15

2. Abstract...18
3. Introduction...19
4. Methods...21

4.1. Patients...21
4.2. Clinical Data...22
4.3. Infection Groups...22
4.4. Statistical Analysis...23

5. Results...25
6. Discussion...28
7. References...34
8. Tables and Figures...42
9. Public Health Implications and Possible Future Directions...49
10. Appendix...51

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