Culture of Cryptococcus neoformans in the nonencapsulated state.

Forty-one strains of Cryptococcus neoformans were examined after 3 days growth on a fresh and aged medium at pH 5 & pH 7 for comparison of capsule formation. Over one-half of the strains did not form visible capsules on aged medium at pH 5. Serotypes and source of isolation did not correlate with ability or inability to form capsules. Growth of C. neoformans in the nonencapsulated state makes it possible to culture many strains of C. neoformans in the form that more closely simulates the true infectious particles.