@skylark1 - Cynthia the reason it is so vital to concretely identify MAC or NTM (Non-tubercular mycobacteria) of which it is a subset, is that it is slow-growing, often antibiotic-resistant, extremely difficult to eradicate and does not respond to typical antibiotics. Treatment is generally by a combination of antibiotics for a long period of time, 18 months to 2 years is not unusual. It is becoming more widely known, but still not understood, so even some pulmonologists have limited experience. I would suggest you do some more reading and arm yourself with a lot of questions, then if MAC is diagnosed be sure your doc is experienced in treating it or ask to be referred to one who is. I recently changed pulmonologists, and even though the first was experienced with MAC, I learned after the fact that he was a "one-size-fits-all" sort of doc, not open to trying different things if the first one didn't work. So glad I switched, even though I have to drive all the way across our metro area for the new doc.