Extracellular DNase activity of Cryptococcus neoformans and Cryptococcus gattii

Extracellular DNase activity was studied in 73 strains of Cryptococcus neoformans and 12 strains of Cryptococcus gattii. DNase activity was measured by DNase agar clearance with and without Methyl Green. All strains tested showed extracellular DNase activity and no significant difference was found betweenC. neoformans and C. gattii strains. DNase production was higher in strains from clinical origin (average radius of 6.2 mm) than among environmental strains (average radius of 2.9 mm). The extracellular enzyme may be detected by DNA substrate PAGE assays and its molecular weight was estimated at 31 kD. These results suggest that extracellular DNase could be considered as a virulence factor involved in C. neoformans–C. gattii species complex pathogenicity.