Diagnosis of cryptococcosis

Cryptococcus neoformans is an encapsulated yeast that can cause life-threatening infectious diseases in both apparently immunocompetent and immunocompromised hosts in all areas of the world. This pathogenic yeast consists of four serotypes (A, B, C, and D) based on capsular agglutination reactions and three varieties or subspecies (1). Serotype A strains have been named C. neoformans var. grubii, serotype B and C strains were classified as C. neoformans var. gattii and recently considered to be a separate species, Cryptococcus gattii, and serotype D strains were named C. neoformans var. neoformans (2,3). About 95% of cryptococcal infections are caused by serotype A strains, whereas 4% to 5% of infections are caused by either serotype D or serotype B and C strains, depending on geographical location.