Chapter 3 : Ecology of Cryptococcus neoformans

Abstract:

In the past half-century, considerable progress has been made in understanding the ecology of Cryptococcus neoformans and the epidemiology of cryptococcal infections. Among the most significant observations were the division of C. neoformans strains into the varieties neoformans and gattii on the basis of phenotypic, biochemical, and genetic differences; the association of C. neoformans var. neoformans with avian excreta; and the association of C. neoformans var. gattii with eucalyptus trees. This chapter describes the distinctions between the two C. neoformans varieties and reviews the available information on the ecology of this fungal pathogen. C. neoformans strains have been divided into two varieties on the basis of phenotypic, serological, genetic, biochemical, and epidemiological criteria. Sexual reproduction of C. neoformans results in the production of haploid basidiospores. The question of which mode of reproduction is employed by C. neoformans in the environment may be important for a complete understanding of its ecology and pathogenesis. Recently, other C. neoformans characteristics have been suggested to contribute to virulence, including mannitol production and the elaboration of several enzymes that have the potential to degrade tissue, such as proteases and phospholipases.