Inclusion Criteria:  International guideline criteria for nodular-bronchiectatic MAC lung disease, i.e. symptomatic, nodular bronchiectatic lesions seen on thorax radiography and ≥2 positive cultures of the same MAC species or one positive culture from a bronchoalveolar lavage; ≥1 positive MAC sputum cultures must be collected in the previous 4 months; Signed and dated patient informed consent.  Exclusion Criteria:  Fibrocavitary MAC lung disease; Antimycobacterial treatment in the last 6 months; Previous MAC lung disease treatment failure, defined as persistent culture positivity despite >6 months of guideline-recommended treatment; Current clinical relevant asthma or otherwise bronchial hyperresponsiveness that is judged to be a contra-indication for HSi. Current HSi use Former adverse reaction to HSi (note: former HSi use that was stopped due to a lack of clinical improvement is not an exclusion criterium); Hypertonic saline intolerability during the screening test inhalation Diagnosis of HIV; Diagnosis of Cystic fibrosis (CF); Active pulmonary malignancy (primary or metastatic) or any other malignancy requiring chemotherapy or radiotherapy within 6 months before screening or anticipated during the study period; Active pulmonary tuberculosis, fungal or nocardial disease requiring treatment Current use of chronic systemic corticosteroids at doses of 15 mg/day for more than 3 months Prior lung or other solid organ transplant Known or suspected current drug or alcohol abuse, that is, in the opinion of the Investigator, sufficient to compromise the safety or cooperation of the patient.