Trikafta/Kaftrio and Pseudomonas Aeruginosa

Inclusion Criteria: * Definite diagnosis of CF and regular follow up, in accordance with the standard operating procedures in force at the Centres * Homozygous for the F508del mutation (F508del/F508del) in the CFTR gene or heterozygous for the F508del mutation and with a minimal function mutation in the other allele (F508del/minimum function mutation) * Chronically infected with P. aeruginosa (defined as having at least 50% or more sputum cultures positive for P. aeruginosa in the previous year) * Candidates starting treatment with Kaftrio or being treated with Kaftrio (retrospective phase) * Both sexes aged \>12 years * Obtaining informed consent from patients and/or from patients' parents (according to the modalities foreseen by the protocol) Exclusion Criteria: * Patients unable to understand the instructions and information provided and to be able to adequately accept the modalities of the study. * Patients unable to expectorate. * Patients with negative sputum for P. aeruginosa at T0, which in the case of prospective patients corresponds to the time of enrollment.