Which of the following would you include when performing a Gram stain?

• A. Methylene blue
• B. Crystal violet
• C. Carbol fuchsin
• D. Safranin

Answer: (B)

Verified step by step guidance

1. Understand that the Gram stain is a differential staining technique used to classify bacteria into Gram-positive and Gram-negative based on their cell wall structure.
2. Recall the sequence of reagents used in a Gram stain: the primary stain, the mordant, the decolorizer, and the counterstain.
3. Identify that the primary stain in the Gram stain procedure is crystal violet, which initially stains all cells purple.
4. Recognize that methylene blue and carbol fuchsin are stains used in other staining techniques (e.g., methylene blue in simple stains, carbol fuchsin in acid-fast stains), not in the Gram stain.
5. Note that safranin is used as the counterstain in the Gram stain to color Gram-negative bacteria pink/red after decolorization, but it is not the primary stain.