Evaluation of a simplified Guizotia abyssinica seed medium for differentiation of Cryptococcus neoformans.

A simplified Guizotia abyssinica seed medium, eliminating glucose, creatinine, and phosphate, was evaluated for the isolation and presumptive identification of Cryptococcus neoformans. Of 80 isolates of C. neoformans tested, 69 (86%) developed the characteristic brown pigment within 12 h on this medium as against only 5 isolates (6%) on the complete medium. In primary cultures of experimentally seeded specimens of sputum, bronchial aspirate, soil, and pigeon excreta, C. neoformans was recognizable within 3 to 5 days on the modified medium in contrast to the 3 to 8 days required on the complete medium. The results demonstrated that the simplified G. abyssinica seed agar, with or without diphenyl, is superior to the complete medium for the rapid development of the brown pigment by C. neoformans.