Histoplasma capsulatum Variety Farciminosum: A New Combination for Histoplasma farciminosum

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Abstract
Four equine isolates of Histoplasma farciminosum from Egypt were grown on a variety of media in an attempt to induce conidia. Of the various media used, soil extract agar (diluted 25 and 50%) induced conidiation in each isolate. They produced numerous smooth-walled to warty microconidia and a moderate number of tuberculate macroconidia after 10-12 wk of incubation at 30 C. The yeast form of each isolate was obtained by growing the isolates at 37 C on brain heart infusion agar with and without 5% sheep blood. Repeated serial transfers onto fresh medium were necessary for complete conversion. Comparison of the micro- and macroconidia of H. farciminosum with those of H. capsulatum var. capsulatum showed a close relationship. The yeast-form budding cells of H. farciminosum were identical to those of H. capsulatum var. capsulatum. Because of the close similarity of the mycelial as well as yeast forms of H. farciminosum to those of H. capsulatum var. capsulatum, we propose that H. farciminosum be treated as a variety of H. capsulatum rather than as a distinct species.