Evaluation of Inhaled Antibiotics on Bacterial Diversity and Richness in the Cystic Fibrosis Lung

Inclusion Criteria: * Diagnosis of cystic fibrosis confirmed by mutation analysis of the cystic fibrosis transmembrane conductance regulator gene * Sputum or throat swab culture positive for Pseudomonas aeruginosa at or within 6 months of enrollment * Age ≥12 years * Forced expiratory volume in one second (FEV1) 25-90 percent-predicted Exclusion Criteria: * Age \<18 years * Inability to routinely expectorate sputum without induction by hypertonic saline * Inability to provide or withdrawal of written informed consent * History of aminoglycoside sensitivity or adverse reaction to inhaled antibiotics * Serum creatinine ≥ 2.0 mg/dl * Serum blood urea nitrogen (BUN) ≥40 mg/dl * Pregnancy or lactating at screening * History of systemic intravenous anti-Pseudomonal antibiotics within 28 days of enrollment