How do Mycobacteria appear when stained by the Ziehl-Neelsen or Kinyoun methods with a methylene blue counterstain?

When Mycobacteria are stained using the Ziehl-Neelsen or Kinyoun methods, they will appear as bright red rods against a blue background when a methylene blue counterstain is applied. The primary stain used in these methods is a carbol fuchsin, which is a vibrant red dye that binds strongly to the mycolic acid present in the cell wall of Mycobacteria, making them resistant to decolorization with acids. After the application of the counterstain, which is methylene blue, the background and any non-acid-fast bacteria will take on a blue color.

This visual contrast is essential for identifying Mycobacteria under a microscope. The bright red color of the Mycobacteria stands out against the blue, making it easy to distinguish them from surrounding cells. The other options describe colors and backgrounds that do not correspond to the characteristics of Mycobacteria when using these specific staining techniques.