There are several phenotypic and molecular methods for differentiation of Mycobacterium tuberculosis and Nontuberculous Mycobacterial Isolates, but the best one is by Real-Time PCR (read the attached article).
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Generally, NTM as they are commonly known are fast growers within a week on solid media and within days in Liquid media. In settings where PCR is not possible, NTMs can be differentiated by their mucoid, flat colonies appearing within the first week on solid media as against the dry, rough and raised colonies of MTB complex.
In liquid media, they appear turbid at times in clumps, smears from cultures lack the typical serpentine chords of MTB.
Even in smear microscopy, an experience microscopist could differentiate between the slender, beaded, irregular shape of the NTMs as against the strait, uniform rods of MTB.
In addition as a 'blend of old and the new', a smear positive sample that turns out to be MTB Not Detected by GeneXpert is qualified as an NTM and you should be over 70% right.
There are several kits like Mycobacterium CM from Hain Life Sciences further differentiate NTM.
Some NTMs are slow growers too!! U can differentiate them by PCR using HSP65 primers ...They yield a 240kb band after PCR. Otherwise, U can grow them on PNB (p-nitro benzoic acid) slopes instead of LJ...ONly NTM sps grow on PNB slopes...
The attached doc may provide some useful info. for both questions, hope this helps.
Please read:
Utility of MPT64 antigen test for differentiating mycobacteria: Can correlation with liquid culture smear morphology add further value?
Article Utility of MPT64 antigen test for differentiating mycobacter...
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