Ease of Use and Microbial Contamination of Tobramycin Inhalation Powder (TIP) Versus Nebulised Tobramycin Inhalation Solution (TIS) and Nebulised Colistimethate (COLI)

Key Inclusion Criteria: * Provide written informed consent, HIPAA authorization, and assent (as appropriate for minors) prior to the performance of any study-related procedure * Confirmed diagnosis of Cystic Fibrosis (CF) * Male and female patients 6 years of age or older at screening * Forced Expiratory Volume in 1 second (FEV1) at screening (Visit 1) must be at least 25% and less than or equal to 90% of normal predicted values for age, sex, and height based on the NHANES III values (Hankinson, 1999) for patients 18 years of age or greater, and based on values from Wang (Wang 1993) for patients less than 18 years of age. * Documented use of any of the nebulized antibiotics based on local practice: * Tobramycin Inhalation Solution, colistimethate, or Tobramycin Inhalation Powder for at least 1 cycle within the last 6 months or * Colistimethate continuous use for at least 8 weeks within the last 6 months This cycle of treatment (or continuous colistimethate treatment period) is in addition to the treatment cycle during which the subject is being screened. * P. aeruginosa must be present in a sputum or deep cough throat swab culture or bronchoalveolar lavage (BAL) (only for BAL a threshold level of 10\^3 CFU/mL is required) within 6 months prior to screening, and in the sputum or deep cough throat swab culture at screening or rescreening (Visit 1); Key Exclusion Criteria: * History of sputum culture or deep cough throat swab (or BAL) culture yielding Burkholderia cenocepacia complex within 2 years prior to prescreening or sputum culture yielding B. cenocepacia complex at screening (Visit 1) * History of hearing loss or chronic tinnitus deemed clinically significant by the investigator * Serum creatinine 176.8 μmol/L (2 mg/dL) or greater, blood urea nitrogen (BUN) 14.28 mmol/L (40 mg/dL) or greater, or an abnormal urinalysis defined as 2+ or greater proteinuria at screening * Known local or systemic hypersensitivity to aminoglycosides * Regularly receiving more than 1 class of inhaled antipseudomonal antibiotic * Use of any investigational drug within 30 days or 5 half-lives, whichever is longer, prior to screening * Signs and symptoms of acute pulmonary disease, e.g., pneumonia, pneumothorax * Body mass index less than 12 kg/m2 * History of malignancy of any organ system, treated or untreated * Clinically significant laboratory abnormalities (not associated with the study indication) at screening (Visit 1) * Pregnant or nursing (lactating) women, where pregnancy is defined as the state of a female after conception and until the termination of gestation, confirmed by a positive human chorionic gonadotropin (hCG) laboratory test * Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using effective methods of contraception during study treatment.