PHOSPHOLIPASE-ACTIVITY IN CRYPTOCOCCUS-NEOFORMANS - A NEW VIRULENCE FACTOR

Fifty isolates of Cryptococcus neoformans were examined for extracellu lar phospholipase production after inoculation onto egg yolk agar; 49 produced a pericolonial precipitate indicative of phospholipase activi ty. Phospholipase B (PLB), lysophospholipase, and lysophospholipase-tr ansacylase activities were identified by radiometric analysis in super natants from 4 clinical isolates. The ratio of colony diameter to colo ny plus precipitate on agar (Pz) correlated with PLB activity. Phospho lipase production was similar in 12 environmental and 13 clinical isol ates of C. neoformans var. gattii. Environmental strains of C. neoform ans var. neoformans (n = 8) produced more phospholipase at 72 h than d id 17 clinical isolates (mean Pt, 0.57 vs. 0.72; P < .01); however, Pz values were similar at 96 h. Quantitation of cryptococci in the lungs and brains of BALB/c mice inoculated intravenously with 4 strains exp ressing high, intermediate, or low phospholipase activity revealed a c orrelation between phospholipase activity and virulence. Phospholipase s secreted by C. neoformans may be implicated in virulence.