A cold staining method for acid-fast bacilli

The Ziehl-Neelsen method is probably the best known and most frequently used procedure for staining tubercle bacilli. The method requires controlled heating for its success. However, in developing countries, such as India, where most laboratories rely mainly on spirit lamps as a source of heat, the Ziehl-Neelsen method often cannot be carried out because rectified spirit is difficult to obtain. The study describes a cold staining technique that uses the same staining solutions as the conventional Ziehl-Neelsen method. For direct smears, the correlation of results of the cold staining procedure with those of the Ziehl-Neelsen method was 97% and for concentrated smears was 99%. The method described is suitable for use in basically equipped laboratories.