Sino-nasal Inhalation of Colistin in Patients With Cystic Fibrosis and Pseudomonas Aeruginosa Colonization

Inclusion Criteria: * subject has a confirmed diagnosis of cystic fibrosis * detection of P. aeruginosa in nasal lavage (culture) with chronic P.a. colonization of the lung (from day -28) * informed consent of the patients or parents * subject \>= 6 years * subject is able to comply with the inhalation procedures and nasal lavage procedures scheduled in the protocol * women of childbearing potential are only included into the study, if they are using an effective method of birth control during the protocol Exclusion Criteria: * subject has a critical condition defined as: forced expiratory volume at one second \< 30% and / or arterial oxygen saturation \< 93% without O2-substitution; need of O2-substitution * subject had an ear, nose, and throat surgery within 3 months prior to study * subject shows signs of nasal bleeding * subject has an ear drum perforation * subject had an acute rhinosinusitis or a pulmonary exacerbation at study entry with need of additional systemic antibiotic therapy against pseudomonas aeruginosa * subject is unlikely to comply with the procedures scheduled in the protocol * subject has a known allergic reaction to the medication * subject is pregnant or breastfeeding * subject participates in another clinical trial within 30 days prior to study entry or 30 days after end of the study. * systemic (oral or intravenous) antibiotic treatment against P.a. 14 days prior to the inclusion and during the study