Comparison of phospholipase production in Cryptococcus neoformans isolates from AIDS patients and bird droppings

Secreted phospholipase has been recently proposed as a virulence determinant in Cryptococcus neoformans as well as Candida albicans. This issue of cryptococcal phospholipase requires screening of phospholipase production in a larger number of isolates from clinical and environmental sources. In this study we examined phospholipase production in a total of 67 C. neoformans isolates from AIDS patients and bird droppings by using the egg-yolk plate method. Phenoloxidase activity, capsule size and growth at 37 degrees C were also measured in these strains in order to observe a possible relationship between phospholipase production of different C. neoformans strains and its virulence. Four of the 21 AIDS strains at 28 degrees C and 1 at 37 degrees C did not produce phospholipase, respectively. In contrast, 38 and 34 of the 46 bird dropping strains were negative for phospholipase production at 28, and 37 degrees C, respectively. Statistical analysis revealed a significant difference in phospholipase production, capsule size and growth ability at 37 degrees C, but not phenoloxidase activity, between the AIDS and the bird dropping strains. The highly prevalent distribution of phospholipase activity in the AIDS strains suggests a role of the enzyme in invading the host.