Morphology of griseofulvin-resistant isolates of Mongolian variant of Trichophyton schoenleini.

Clinical, experimental and electronmicroscopic observations, and computer-enhanced images were made on 5 patients with tinea favosa resistant to griseofulvin. The pathologic fungus was identified as the Mongolian variant of Trichophyton schoenleini. The results of physical examinations, routine tests of blood, urine and stool, liver and immunologic function examinations were normal in all of the 5 patients. Under scanning electron microscopy, the surface of the spore showed pineapple-like form, the cluster of the acrogenous spores presented flower shape, and the antler-like hyphae appeared twisted in the culture. They were observed by transmission electron microscope and the images were processed by microcomputer. It was found that the cell walls of the fungi consisted of 8 layers, among which the inner layer was loose and contained cytoplasm. It was also found that all structures within the cytoplasm possessed a 1-3 layer intact envelope and there was chromatin in the nucleus. These may be contributing factors in the development of resistance to griseofulvin. This multiple-layered thick cell wall may act as a barrier responsible for the impermeability of the cell of fungi to griseofulvin.