Rapid in vitro capsule production by cryptococci.

Four agar media (blood, corn meal, chocolate, and Sabouraud's) and four liquid media (brain-heart infusion broth, one percent peptone broth, pooled human serum, and lyophilized rabbit coagulase plasma) were evaluated for their ability to enhance the production of capsules from four strains of Cryptococcus yeast within 48 hours at 25C and 35C. The yeast in serum and plasma was washed with distilled water prior to India ink preparation in order to prevent precipitation of the ink. The rabbit coagulase plasma was the only medium which consistently produced large capsules in 48 hours. Incubation temperatures and anticoagulant made little difference.