Which sequence is correct for Ziehl-Neelsen staining?

Study for the CAMLPR Histology Practice Test. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

Multiple Choice

Which sequence is correct for Ziehl-Neelsen staining?

Explanation:
The staining sequence tests how acid-fast organisms resist decolorization due to their waxy cell wall rich in mycolic acids. Begin with the primary stain, carbol fuchsin, often helped by heat to drive dye into the robust cell wall. Then apply an acid-alcohol decolorizer; acid-fast organisms keep the red dye, while non–acid-fast organisms are decolorized. Finally, apply a counterstain such as methylene blue to color the now-decolorized cells, so non–acid-fast bacteria appear blue while acid-fast bacteria remain red. This order—carbol fuchsin, acid alcohol, methylene blue—produces the differential result. Starting with a counterstain or decolorizing before staining would not achieve the same distinction, and the primary stain must come first to determine which cells retain dye after decolorization.

The staining sequence tests how acid-fast organisms resist decolorization due to their waxy cell wall rich in mycolic acids. Begin with the primary stain, carbol fuchsin, often helped by heat to drive dye into the robust cell wall. Then apply an acid-alcohol decolorizer; acid-fast organisms keep the red dye, while non–acid-fast organisms are decolorized. Finally, apply a counterstain such as methylene blue to color the now-decolorized cells, so non–acid-fast bacteria appear blue while acid-fast bacteria remain red. This order—carbol fuchsin, acid alcohol, methylene blue—produces the differential result. Starting with a counterstain or decolorizing before staining would not achieve the same distinction, and the primary stain must come first to determine which cells retain dye after decolorization.

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