Staining, Histochemistry and Histotechnology
(Frequently Asked Questions)
Dr. John A. Kiernan
Department of Anatomy
and Cell Biology
The University of Western Ontario
stain for anthrax bacilli
What is M'Faydean's stain?
[This has been put together from three replies to a question raised on the HistoNet
M'Faydean's stain is a simple stain using any well polychromed methylene blue (e.g. aged Loefflers). It is applied to heat-fixed smears for 10-30 seconds.
Polychroming (demethylation) is traditionally achieved by exposure of Loeffler's soln. to light and air for several months until it acquires a purplish tinge. However the oxidation process can be accelerated by application of heat as in Unna's method. (G. Gurr, 1963 p. 88 & 91); also E. Gurr, 1960, pp. 264-268).
Loeffler's methylene blue:
Methylene blue 0.5 g
1% w/v Aq. KOH 1.0 ml
Ethanol 30.0 ml
D.water 70.0 ml
Warm the water to 50 C., stir in methylene blue and add other ingredients, cool and
filter before use.
Polychrome methylene blue (Unna):
Methylene blue 1.0 g
Pot. carbonate 1.0 g
Ethanol 20.0 ml
D.water 100 ml
Dissolve methylene blue in water, add
pot. carb. and alcohol, place in boiling water bath
and evaporate to 100 ml.
Any other polychrome methylene blue formulation should work well also.
Results: Bacilli appear Navy Blue with Anthax showing a narrow area (capsule) around and between bacilli that is reddish purple (metachromatic). A strong word of warning: many species of bacillus may also be encapsulated, e.g. Cereus etc. If you produce any positives get them confirmed at a Reference Microbiology Lab. for Infectious Diseases, or try the Armed Forces Institite of Pathology.
Gurr doesn't give any further references in his book as to McFadyean, whether the method was published or by personal communication.
"Encyclopedia of microscopic stains," by Edward Gurr. London: Arnold, 1960. (pp 264-268)
"Biological Staining Methods." by George T. Gurr. 7th Edition. 1963. (Published by George T. Gurr Ltd. 136-144, New King's Road, London, S.W.6.)
Australian Biostain P/L