Hi there!
MAC stands for Mycobacterium Avium Complex. It is a group of 12 bacteria. MAI, Mycobacterium avium-intercellulare, is one of the bacteria in that group. The confusing part is that some medical professionals often use the terms "MAC" and "MAI" interchangeably.

Many laboratories do not have the ability to "sub-speciate" to determine which of the 12 MAC bacteria is infecting a person. That is why samples are often sent to higher-level labs like the ones at the Mayo, National Jewish Health and UT Tyler.

When I had a bronchoscopy in 2018, a sample was sent to National Jewish for sub-speciation and it was determined that the bacteria was m. intercellulare (MAI). So, in my case, the term MAI was not being used in a general sense, but rather based on my lab analysis.

Although I was able to clear the bacteria without antibiotics, if I had opted for the 3-drug treatment, it would have been identical to those being treated for m.avium, another bacterium in the Complex.

I hope this is helpful.
Linda Esposito