A revaluation of the use of conventional Ziehl-Neelsen stain for detection of non-tuberculous mycobacteria

Detection of non-tuberculous mycobacteria is difficult and not always consistent. These organisms are emerging as opportunistic pathogens in a number of clinical conditions, in part due to their remarkable stress intolerance. The Ziehl-Neelsen stain is optimal for the detection of Mycobacterium tuberculosis complex but is less reliable for the detection of non-tuberculous mycobacteria when using acid-alcohol as a decolouriser. Acid alcohol decolourisation should not be relied on where non-tuberculous mycobacteria are suspected, or the possibility of dormant forms of mycobacteria exists. In those instances other decolourisation methods should be considered, such 20-25% sulphuric acid or Gabbett's methylene blue. Keywords: mycobacteria, Ziehl-Neelsen stain, non-tuberculous mycobacteria, mycobacteria staining methods, basic fuchsin. NZJ Med Lab Sei 2019; 73:93-94