Which statement is true about Kinyoun and Auramine-Rhodamine staining methods?

• A. Both contain phenol
• B. Both lack phenol
• C. Only one contains phenol
• D. Neither contain phenol

Answer: (A)

Phenol is used in both staining methods to help the dye penetrate the lipid-rich, waxy cell wall of mycobacteria and to stabilize the stain during washing.

In the Kinyoun (cold) acid-fast method, phenol is a key part of the carbolfuchsin solution, acting as a solvent that allows the dye to enter the mycobacterial wall without applying heat. This enables reliable staining at room temperature.

In the Auramine-Rhodamine fluorochrome method, phenol is included with the fluorochromes to dissolve and carry the dyes into the cells, enhancing uptake and bright fluorescence under the appropriate light.

Because both approaches rely on phenol to facilitate dye entry and retention in the waxy cell envelope, the statement that true describes both methods is that they both contain phenol.