Fite Faraco
for Acid Fast Bacteria

Solutions

Ziehl's Carbol fuchsin
1% aqueous hydrochloric acid
Methylene blue, 0.1% aqueous
Dewaxing Mixture
Xylene
Vegetable oil
 
2 volumes
1 volume (peanut, cottonseed, olive)

Tissue sample
5µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are usually satisfactory.

Method

  1. Remove wax with the dewaxing mixture, two or three changes over 20 minutes.
  2. Blot the section dry with filter paper, and rinse with water.
  3. Repeat the blotting and rinsing until the section is wetted by the water.
  4. Place sections on a staining rack and gently cover each section with filter paper soaked in carbol-fuchsin, then do either of the following:
    A)
    1. Pour carbol-fuchsin onto each section until the slide is full.
    2. Grip a cotton ball in long forceps, and dip into absolute ethanol.
    3. Cover all inflammable fluids, then ignite the cotton ball.
    4. Move the flame under the sections as evenly as possible.
    5. Heat until the carbol-fuchsin steams.
    6. Leave five minutes.
    7. Repeat the heating and leave for a further five minutes.
    B)
    1. Put some carbol fuchsin in a small Erlenmeyer flask.
    2. Heat on a hot plate until it almost boils.
    3. Pour onto each slide, ensuring each section is covered.
    4. Leave five minutes.
    5. Repeat, and leave for a further five minutes.
  5. Wash off the carbol-fuchsin with cold water, removing the filter paper.
  6. Clean the back and around the tissue with an ethanol soaked tissue to remove any carbol-fuchsin deposits.
  7. Decolorise with acid water until dye ceases to be removed. The section should be pink, but will be darker than with a Ziehl-Neelsen.
  8. Wash well with cold water.
  9. Place in methylene blue solution 10-15 seconds.
  10. Wash with cold water until pale blue.
  11. Dehydrate quickly with ethanol.
  12. Clear with xylene and mount with a resinous medium.

Expected results

Notes

  1. If using method B, do not heat the carbol-fuchsin in a test tube with a bunsen burner as it may unexpectedly spurt when it reaches boiling.
  2. The Fite Faraco differs from the Wade Fite in the mixture used for dewaxing. Otherwise they are the same.

 

Reference
Drury, R.A.B. and Wallington, E.A., (1980)
Carleton's histological technique Ed. 5
Oxford University Press, Oxford, UK.

 


 

 

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