There are hundreds of Mycobacteria species, and even more subspecies, so terminology gets confusing REALLY quickly. Worldwide, the most common are M. tuberculosis (TB) M. bovis (Bovine TB) & M. leprae (Leprosy.)

Then there are the species that we talk about here, NTM or non-tubercular mycobacteria, which, in spite of how active this group is, are quite rare (maybe 100,000 - 200,000 people per year) M. avium and M. intracellulare are the most common NTM, and have a number of further distinctions (subspecies.) M. aviums & M. intracellulare are often referred to interchangeably as MAC or MAI as they are closely related, and the diagnosis and treatment are very similar. There are other, less common species, some of which can cause even more serious infection than MAC, M. abscessus is one. And a few that may be present along with MAC but are not considered risky to humans.

So what exactly do we need to know? Mycobacteria can be SEEN on a slide in the lab, using an alcohol/acid precipitant on the slide. That is what the initial "positive AFB" lab results mean. At that point we know there is some Mycobacteria present in the sputum sample - but not which one, in what quantity, and whether it is one that needs to be treated.

So, an AFB positive specimen is sent to a lab that does a culture (grow it in a special medium for several weeks) to see how much bacteria grows. Once it has grown, the specific species & subspecies, can be identified. Next, recommended antibiotics are applied to the culture to see which ones kill your specific bacteria.

Wait, we're not quite done yet! Finally, your doctor evaluates the test results, your other symptoms, the severity of infection in your lungs, and your overall health to determine whether to begin treating you with antibiotics.

I bet that's a lot more than you wanted to know, but I hope it helps you understand why it takes so long to figure out what to do. The good thing is, MAC/MAI grow VERY slowly, so a delay in beginning treatment is not dangerous to you.

What stage are you at in the diagnostic process? Have you also been diagnosed with bronchiectasis?
Sue