A Medium for the Growth and Maintenance of the Yeast-like Phase of Histoplasma capsulatum

Abstract

The production and maintenance of the yeast-like phase of Histoplasma capsulatum is known to be difficult. Numerous media have been recommended such as blood agar (Conant, 1941) and Francis' cystine glucose agar (Campbell, 1947). These solid agar modifications have, however, a disadvantage in that transfers must be made at short intervals and the yeast-like phase is not obtained consistently. During recent experiments, in an attempt to obtain the yeast-like phase of H. capsulatum, the egg-yolk-potato medium commonly used for the growth of Mycobacterium tuberculosis was found to be of value. Twenty-three strains of H. capsulatum wrhich were ob? tained from Vanderbilt University were found to develop a yeastlike phase on this medium within one to two transfers if grown at 37? C. These cultures have maintained their yeast-like phase on repeated subculture for a minimum period of thirty days. The formula and preparation of the egg-yolk-potato medium (Sasano and Medlar, 1943) is as follows: