Pathogenicity of basidiospores of Filobasidiella neoformans var. neoformans

Basidiospores of Filobasidiella neoformans var. neoformans (progeny of Cryptococcus neoformans MT 100·1 × VR 45980) were able to induce cryptococcosis in Swiss albino mice if inoculated by intraperitoneal injection, nasal instillation or nasal spraying. The latter method, with the aid of a jet nebulizer, was first adopted to imitate the natural entrance of infectious particles. Using this method the small number of basidiospores (7 × 103) could induce cryptococcosis in mice, whilethe higher number of the parental laboratory-grown yeast cells (1·5 × 106) did not produce infections. By nasal instillation Cyclophosphamide (Cy)-treated mice were more susceptible to the basidiospores, showing 80% cryptococcosis (eight of 10). Seven of the eightinfected mice had disseminated cryptococcosis. Immunocompetent mice were more resistant to basidiospore infection than Cy-treated mice, as 40% of that group developed only pulmonary cryptococcosis; none had disseminated infection. Thus, we propose that basidiospores are one form of the infectious propagules of F. neoformans var. neoformans whichcan cause cryptococcosis, particularly in immunocompromised people.