Special Stains - Wade Fite Technique

The Wade Fite special stain is a modification of Z.N. method. This is used to demonstrate M leprae which is much less acid-and alcohol-fast than the tubercle bacillus. The procedure is varied by avoiding putting the section through ethanol which would remove the M leprae bacterium by the use of xylene/vegetable oil mixtures, sulphuric acid to replace the acid alcohol and heat at the end. This special stain is less commonly used but can still be useful for diagnosis.

The main method for carrying out this technique is listed below

1. Deparaffinise sections in 2 changes Xylene-Vegetable oil (2:1 ratio) for 6 minutes each.

2. Blot dry using filter paper, then wash in water for 5 minutes

3. Place carbol fuchsin solution onto slides. Leave for 30 minutes

4. Wash well in distilled water

5. Differenciate using 5% sulphuric acid in 2.5% alcohol until no more colour can be removed. Sections are pale pink.

6. Wash in distilled water

7. Counterstain in 1% methylene blue dilution 1 in 10 with distilled water for 30 seconds

8. Wash in water

9. Blot dry then place in 56°C oven for 5 minutes to dry off.

10. Once dry, quick dip in xylene and mount.

Result

Mycobacterium Leprae	Pink/Red
Nuclei and background	Blue

Photo x10 Wade Fite