Which reagents constitute the Brown and Hopps staining reagents?

• A. Acetone, crystal violet, and picric acid
• B. Ethanol, safranin, and acetic acid
• C. Methanol, carbol fuchsin, and iodine
• D. Acetone, methylene blue, and potassium permanganate

Answer: (A)

Brown-Hopps staining is a Gram-type technique used on tissue sections to visualize bacteria. It relies on acetone as the decolorizing solvent, crystal violet as the primary stain to color all bacteria, and picric acid as the counterstain to provide a contrasting background. The combination yields Gram-positive organisms that remain purple while Gram-negative organisms take on the yellow counterstain, making it easier to identify bacteria within the tissue.

Other reagent sets use different decolorizers or counterstains (for example, ethanol or methanol with safranin or carbol fuchsin, or dyes like methylene blue), which are not part of the Brown-Hopps protocol.