| histoplasma | A fungus found worldwide. In the USA, it is so common in the midwest that in parts of kentucky and tennessee nearly 90% of adults show evidence of exposure (with a positive histoplasma skin test). (12 Dec 1998) |
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| Histoplasma capsulatum | A dimorphic fungus species of worldwide distribution that causes histoplasmosis in humans and other mammals; its ascomycetous state is Ajellomyces capsulatum. The organism's natural habitat is soil fertilised with bird and bat droppings, where it grows as a mold, fragments of which, following inhalation, produce the primary pulmonary infection; within the mammalian host tissues, inhaled mycelial fragments grow as uninuclear yeasts that reproduce by budding. This parasitic form may also be induced in the laboratory by culturing the mycelial phase at 37캜 on a blood-enriched medium; growth reverts to the mycelial form when the temperature is below 37캜. Histoplasma capsulatum var. Duboisii causes a clinically distinct disease, African histoplasmosis, in which large yeast cells with thicker walls are found in tissues, in contrast to the small yeast cells of Histoplasma capsulatum var. Farciminosum, which causes epizootic lymphangitis. Origin: histo-+ G. Plasma, something formed (05 Mar 2000) |