Inclusion Criteria:

* CF as diagnosed by:

1. Documented sweat chloride greater than or equal to 60 mEq/L by quantitative pilocarpine iontophoresis test; or
2. Two well-characterized genetic mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene; or
3. Abnormal nasal potential difference with accompanying symptoms characteristic of CF.
* PA present in expectorated sputum or throat swab culture at Screening.
* Participants must have received three or more courses of TIS within the previous 12 months.
* Participants on chronic azithromycin must have had no change in regimen in the previous 3 months and must have had a need for TIS and/or additional antipseudomonal therapy since initiation of azithromycin.
* Forced expiratory volume in 1 second (FEV1) between (and including) 25% and 75% predicted at Screening.
* Ability to perform reproducible pulmonary function tests.
* Arterial oxygen saturation (SaO2) greater than or equal to 90% on room air at Screening.

Exclusion Criteria:

* Current use of oral corticosteroids in doses exceeding the equivalent of 10 mg prednisone a day or 20 mg prednisone every other day.
* History of sputum or throat culture swab yielding Burkholderia cepacia in the past 2 years.
* History of daily continuous oxygen supplementation or requirement for more than 2 liters/minute at night.
* Administration of any investigational drug or device within 28 days of Screening (Visit 1) or within 6 half-lives of the investigational drug (whichever was longer).
* Known local or systemic hypersensitivity to monobactam antibiotics.
* Inability to tolerate inhalation of a short acting Beta-2 agonist.
* Changes in antimicrobial, bronchodilator, anti-inflammatory, or corticosteroid medications within 7 days before Screening or between Screening and the next visit.
* Changes in physiotherapy technique or schedule within 7 days before 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 or serum chemistry at Screening (aspartate aminotransferase \[AST\], alanine aminotransferase \[ALT\] greater than 5 times the upper limit of normal range; Creatinine greater than 2 times the upper limit of normal range).
* Positive pregnancy test at Screening.
* Female of childbearing potential who was lactating or in the opinion of the investigator was not practicing acceptable birth control.
* 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.