My understanding is that in regards to AFB (acid fast bacteria) such as MAC a colony of bacteria on a culture plate can arise from a single bacteria or maybe just a very few. Most labs will just give you a positive or negative on the AFB test (the test that takes 4-8 weeks to complete). I know that NJH (National Jewish Health) and Mayo does do it, but at Mayo I would always have to request the count. I have had 2 positives of Mycobacterium abscessus over the last 3 years, one of them was only 1 colony and the other 2. The pulmonologist in each case was not concerned and suggested it was only "colonizing" not "infecting" my lungs. Hope this helps. Bill