Antibiotic sensitivity of the yeast and mycelial phases of Histoplasma capsulatum.

Cycloheximide and chloramphenicol in combination have a greater effect on yeast cells of Histoplasma capsulatum than on the mycelial phase of this fungus. In contrast, clotrimazole was found to be more effective against mycelia. Miconazole produced a pronounced effect against both phases wheras tolnaftate was only slightly active. Sulfadiazine and griseofulvin were completely inactive against both phases. The differential sensitivities of the 2 phases of H. capsulatum to various antibiotics can be useful in studying the transition of the dimorphic fungus from 1 phase to the other.