I'm VERY curious about what you hear. MAI cannot be diagnosed by CT as far as I am aware, but someone else may know something I do not. NTM/MAC/MAI is a very slow-growing bacteria related to TB, and is diagnosed through a culture grown out in a specialized lab. The process takes at least 6 weeks, and for proper treatment is followed by exposing the bugs to various combinations of antibiotics to see what will treat your strain. The sample may be procured via a cough, or a bronchoscopy. There are other bugs that can cause the pneumonia as well. I was treated for pseudomonas pneumonia after cultures were taken (that culture only takes 2-3 weeks, and usually a shorter course of treatment - mine was 2 months with Levaquin, then inhaled Tobramycin). Then the second set of cultures came back confirming MAC and I have been on that treatment over a year, first 3 times weekly, now daily. My husband, who also has bronchiectasis, had neither pseudomonas nor MAC, but yet another bacterial pneumonia (I don't remember specifically) and was treated with 4 courses antibiotics (2 different ones at different times.)