Mycobacteria (or AFB/Acid Fast Bacteria) are difficult to stain because of the high proportion of lipid and wax in their cell walls. Up to now, in order to carry out the classical Ziehl-Neelsen staining, the test material has had to be heated with carbolfuchsin solution to produce the mycolic acid acid/fuchsin compound.

Tb-color offers a modified Ziehl-Neelsen staining which works without heating (Kinyoun method). Pre-treatment with Sputofluol® frees the bacteria from the surrounding sputum and cell material, killing unwanted microorganisms at the same time.

Once stained, acid acid-fast mycobacteria keep retain their colouring even after treatment with strong decolourizing solutions as HCl-ethanol. They remain red after counterstaining with malachite green, whereas the microorganisms susceptible to acid take on the green.

Merck's Tb-color staining set uses the modified Ziehl-Neelsen staining procedure and eliminates the necessity of heating the carbolfuchsin solution, thus preventing the release of phenol vapour.

As sample materials are suited for use include Sputofluol®-pretreated smears of sputum, FNAB, lavages, imprints, body fluids, exudates, puss, liquid, and solid cultures. lAll sample materials must be heat-fixed carefully.

The smears can be stained on a staining rack, in coplin jars or in a staining instrument acc. to the protocol. Acid-fast bacteria appear magenta red and the background is light green.

Advantages of this convenient kit include:-

• no heating of carbolfuchsin solution
  
• effective pretreatment for high-contrast visualization of mycobacteria
  
• good sensitivity and specificity of the method