AN IMPROVED CULTURE-MEDIUM FOR DETECTING LIVE YEAST PHASE CELLS OF PARACOCCIDIOIDES-BRASILIENSIS

The plating efficiency of standard mycological media such as brain hea rt infusion (BHI) agar is poor for Paracoccidioides brasiliensis. We p repared a water-extract of yeast phase cells of P. brasiliensis and ex amined it for growth-enhancing activity for the fungus. The water-extr act, when added to BHI agar to a concentration of 5%, improved the pla ting efficiency of the medium for the fungus to some extent, but the d egree of improvement was considerably varied among P. brasiliensis iso lates. By contrast, when the water-extract was added in combination wi th horse serum (4%), the plating efficiency was highly improved (to 94 -99%) for all the P. brasiliensis isolates employed. The growth-enhanc ing factor(s) in the water-extract was heat-stable and heating at 120- degrees-C for 15 min had little, if any, effect on growth-enhancing ac tivity.