McFadyean reaction

Principle

Polychrome methylene blue stains the capsule of Bacillus anthracis pink-purple, while the bacilli appear blue.

Procedure

• Air-dry a thin smear of blood or tissue fluid; fix gently.
• Stain with polychrome methylene blue for about 1 minute; rinse, dry and examine.

Results

• Blue, square-ended bacilli in short chains surrounded by pink-purple capsular material

Safety

Suspected anthrax is handled under biosafety level 3 conditions and reported to public health.