Hi all. please I badly need help about the acid fast staining technique for Mycobacterium smegmatis or Mycobacterium phlei as they both give me varying response to staining and in many cases they appear purple not red unfortunately. I'll be using them for training undergraduate students in the acid fast staining. Thank you all in advance

Hello

Without more information it is difficult to know your problem ie what stain are you using.

It is also possible that nothing is wrong with your stain. Assuming it is a standard ZN stain many NTM will appear very dark compared to MTB. Try mixing non AFB with your stain then you could compare the difference in staining.