OPTIMIZing Treatment for Early Pseudomonas Aeruginosa Infection in Cystic Fibrosis

The purpose of this trial is to compare the effects of treatment with tobramycin solution for inhalation (TIS) with and without azithromycin in people with cystic fibrosis (CF) age 6 months to 18 years who have early isolation of Pseudomonas aeruginosa (Pa) from a respiratory culture. Specimens of blood and sputum or throat swabs will be taken during the study along with pulmonary function testing. Participants will receive initial treatment with TIS followed additional treatment with TIS if quarterly respiratory cultures are positive for Pa in addition to either azithromycin or placebo for 18 months.