A Culture Medium for the Primary Isolation of Fungi

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Abstract
A new agar culture medium for the primary isolation of pathogenic fungi is reported to inhibit the growth of Gram-pos. and Gram-neg. bacteria while supporting the growth of fungi as small, discrete, non-spreading colonies. The completed medium contains in dist. water 1% dextrose, 1% granular peptone, 1.5% dehydrated oxgall, 2% agar (all Bacto grade, Difco Laboratories), and 0.001% crystal violet (91% dye content, used in 5% alcoholic soln.). No pH adjustment is required. Sterilization was accomplished at 10-12 lbs. pressure (115-117.7[degree]C.) for 15 min. and the agar was cooled to approx. 46[degree]C before adding sufficient streptomycin sulfate to provide a final conc. of 30 U. of the antibiotic/ml. of medium. The inhibitory action of the poured medium to Gram-pos. and Gram-neg. bacteria was found to be unaltered by several weeks'' storage at room temp. and 37[degree]C. Growth of 22 spp. of common pathogenic fungi and 11 spp. of saprophytic fungi as well as numerous aerial saprophytic types was found to be unaffected by the streptomycin in the conc. employed. Initiation of growth of these fungi on the new medium was at a rate comparable with Sabouraud dextrose agar. Nocardia asteroides did not grow because of sensitivity to streptomycin. Preliminary studies indicate that the new medium holds considerable promise as a diagnostic tool for the primary isolation of fungi from specimens possessing a mixed bacterial and fungal flora such as feces, sputum, exudates, skin scrapings, hair, abscess material, etc.

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