Ultrastructure of Trichophyton mentagrophytes stained with neutral red.

The ultrastructure of Trichophyton mentagrophytes cells stained with neutral red was investigated using electron microscopy and X-ray microanalysis. Fixatives containing molybdenum and chromium were used to prevent the outflow of neutral red. Electron-dense particles composed of metals and dye were observed exclusively in the vacuoles, which were increased in number and size, but not near the cell wall. Results indicate that neutral red passes directly through the fungal cell wall and is incorporated into the vacuoles.