Spore stain (Schaeffer-Fulton)

Principle

Bacterial endospores have tough coats that resist ordinary stains. Heated malachite green enters the spore; water removes it from the vegetative cell, which is then counterstained with safranin.

Procedure

• Fix the smear; cover with malachite green and steam for about 5 minutes (keep it moist).
• Rinse with water; counterstain with safranin for 30 s; rinse and dry.

Results

• Spores: green
• Vegetative cells: red

Use

Shows spore position (central, subterminal, terminal) and swelling, helpful for Bacillus and Clostridium (e.g. terminal 'drumstick' spores of C. tetani).