Hi pink - Any other symptoms? Like cough, with or without sputum, chest pain, fatigue, fever, shortness of breath, weight loss... Absent any other symptoms, my pulmonologist chooses to wait and watch (closely), but with symptoms he treats.
MAC grows slowly, so he said the downside of waiting and watching is minimal. In my case, I had multiple symptoms, as well as evidence of expanding nodules, so we are treating.
Although this reatment regimen is not pleasant, I have to admit I feel better, and just survived a major cold with lung involvement without requiring additional antibiotics or hospitalization - just additional rest and nebuliser treatments - something that I have not been able to manage for several years.
The +1, +2, etc diagnosis has been used in wound care and TB testing to quantify the amount of bacteria detected. In past, it was used to determine whether or not to treat, but now doctors tend to treat if there is evidence of infection and symptoms...
I will reiterate what others have said - make sure your lung doc is experienced with bronchiectasis, and if not, find someone who is.