Which statement best describes Lactophenol Cotton Blue stain as used in mycology?

Which statement best describes Lactophenol Cotton Blue stain as used in mycology?

• A. It is used only for bacterial staining
• B. It permanently fixes slides
• C. It stains fungal structures blue
• D. It is fungicidal and sporicidal

Answer: (D)

Lactophenol Cotton Blue works as both a staining medium and a fixative/disinfectant because of its components. Cotton blue stains fungal structures blue by binding to chitin in the cell walls, making hyphae and spores visible. The phenol in the solution acts as a fixative and antimicrobial agent, which gives the stain fungicidal and sporicidal properties. This biocidal action is a practical consequence of using the stain and influences how slides are handled, since the organisms are killed in the process. That combination—coloring fungal elements blue and simultaneously killing the material—makes the statement about being fungicidal and sporicidal the most accurate description. The other points are less descriptive: it’s not for bacteria, it’s not used as a permanent fixative for slides, and while it does stain blue, the biocidal aspect is the defining feature in this context.

Lactophenol Cotton Blue works as both a staining medium and a fixative/disinfectant because of its components. Cotton blue stains fungal structures blue by binding to chitin in the cell walls, making hyphae and spores visible. The phenol in the solution acts as a fixative and antimicrobial agent, which gives the stain fungicidal and sporicidal properties. This biocidal action is a practical consequence of using the stain and influences how slides are handled, since the organisms are killed in the process. That combination—coloring fungal elements blue and simultaneously killing the material—makes the statement about being fungicidal and sporicidal the most accurate description. The other points are less descriptive: it’s not for bacteria, it’s not used as a permanent fixative for slides, and while it does stain blue, the biocidal aspect is the defining feature in this context.