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تسجيل

Morphology and Identification of Cryptococcosis

المؤلف:  Stefan Riedel, Jeffery A. Hobden, Steve Miller, Stephen A. Morse, Timothy A. Mietzner, Barbara Detrick, Thomas G. Mitchell, Judy A. Sakanari, Peter Hotez, Rojelio Mejia

المصدر:  Jawetz, Melnick, & Adelberg’s Medical Microbiology

الجزء والصفحة:  28e , p704

2026-02-18

458

In culture, Cryptococcus species produce whitish mucoid colonies within 2–3 days. Microscopically, in culture or clinical material, the spherical budding yeast cells (5–10 µm in diameter) are surrounded by a thick nonstaining capsule (see Figure 1). All species of Cryptococcus, including several nonpathogenic species, are encapsulated and possess urease. However, C. neoformans and C. gattii differ from nonpathogenic species by the abilities to grow at 37°C and the production of laccase, a phenol oxidase, which catalyzes the formation of melanin from appropriate phenolic substrates (eg, catecholamines). Both the capsule and laccase are well-characterized virulence factors. Clinical isolates are identified by demonstrating the production of laccase or a specific pattern of carbohydrate assimilations. Adsorbed antisera have defined five serotypes (A–D and AD); strains of C. neoformans may possess serotype A, D, or AD; and iso lates of C. gattii may have serotype B or C. In addition to their capsular serotypes, the two species differ in their genotypes, ecology, some biochemical reactions, and clinical manifestations. Sexual reproduction can be demonstrated in the laboratory, and successful mating results in the production of mycelia and basidiospores; the corresponding teleomorphs of the two teleomorphic species are Filobasidiella neoformans and F. bacillispora.

Fig1. Cryptococcosis. The capsule of C. neoformans is notably apparent in this pulmonary lavage specimen. Giemsa’s stain. 1000×.