International Safety and Efficacy Study of Aztreonam for Inhalation Solution (AZLI) in Cystic Fibrosis Patients With P. Aeruginosa

Inclusion Criteria: * Documentation of CF diagnosis as evidenced by one or more clinical features consistent with the CF phenotype and one or more of the following criteria: * Sweat chloride greater than or equal to 60 mEq/L by quantitative pilocarpine iontophoresis test (QPIT); * Two well-characterized mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene; or * Abnormal nasal potential difference. * PA present in expectorated sputum or throat swab culture at Screening. * FEV1 between (and including) 25% and 75% predicted at Screening. * Negative pregnancy test at Screening. * Ability to perform reproducible pulmonary function tests. * Arterial oxygen saturation (SaO2) greater than or equal to 90% on room air at Screening. * Ability to provide written informed consent. Exclusion Criteria: * Administration of antipseudomonal antibiotics by inhalation, IV, or oral routes (including azithromycin) within 14 days of Screening. * Current use of oral corticosteroids in doses exceeding the equivalent of 10 mg prednisone/day or 20 mg prednisone every other day. * History of sputum or throat swab culture yielding Burkholderia cepacia in the previous 2 years. * History of daily continuous oxygen supplementation or requirement for more than 2 liters/minute at night. * Administration of any investigational drug or use of any investigational device within 28 days of Screening and within 6 half-lives of the investigational drug (whichever was longer). * Known local or systemic hypersensitivity to monobactam antibiotics. * Inability to tolerate short-acting bronchodilator use at least three times daily. * Changes in protocol-permitted antimicrobial, bronchodilator, anti-inflammatory, or corticosteroid medications within 7 days prior to Screening or between Screening and the next visit. * Changes in physiotherapy technique or schedule within 7 days prior to Screening or between Screening and the next visit. * History of lung transplantation. * A chest x-ray indicating abnormal findings at Screening or within the previous 90 days. * Abnormal renal or hepatic function at Screening. * Any serious or active medical or psychiatric illness which, in the opinion of the investigator, would have interfered with participant treatment, assessment, or compliance with the protocol. * Use of aerosolized hypertonic saline (except for sputum induction) during the 14 days preceding Visit 1.