I have had Bronchiectasis since around 2001. As far as i know i do not have MAC. But the sputum testing for it does not always reveal it. People seem to say a Bronchoscopy is how they found it. Things i do or have read about to prevent it are: Nebulizing with Saline, Taking baths instead of showers, Not digging in the dirt or gardening or at least wear a good mask if you do, boiling water for 10 minutes or using spring water or using a LifeStraw pitcher that filters it out, masking when you vacuum or clean dust etc. Of course keeping your immune system strong with vitamin D3 etc.