Cryptococcus gattii infection: Microbiology, epidemiology, and pathogenesis
- Sharon Chen, PhD, MBBS, FRACP, FRCPA
Sharon Chen, PhD, MBBS, FRACP, FRCPA
- Clinical Associate Professor
- Sydney Medical School, University of Sydney
- Kieren A Marr, MD
Kieren A Marr, MD
- Section Editor — Compromised Host Infections; Fungal Infections
- Professor of Medicine and Oncology
- Johns Hopkins University School of Medicine
- Tania C Sorrell, MD
Tania C Sorrell, MD
- Professor of Clinical Infectious Diseases and Director of the Centre for Infectious Diseases and Microbiology
- Sydney Medical School, University of Sydney
Cryptococcus gattii is a fungal pathogen that is endemic in the tropics and subtropics and that has also caused an outbreak that is ongoing in British Columbia, Canada, and the United States Pacific Northwest; C. gattii is genetically and biochemically distinct from Cryptococcus neoformans [1-3]. Together, C. gattii and C. neoformans account for most cases of cryptococcal infections in humans, although C. neoformans is far more common. Like C. neoformans, infection with C. gattii manifests most often as meningoencephalitis and/or pneumonia.
The microbiology, epidemiology, risk factors, and pathogenesis of C. gattii infection will be reviewed here. The clinical features, diagnosis, and treatment of C. gattii infection are discussed separately. C. neoformans infection is also reviewed elsewhere. (See "Cryptococcus gattii infection: Clinical features and diagnosis" and "Cryptococcus gattii infection: Treatment" and "Microbiology and epidemiology of Cryptococcus neoformans infection" and "Epidemiology, clinical manifestations, and diagnosis of Cryptococcus neoformans meningoencephalitis in HIV-infected patients" and "Clinical manifestations and diagnosis of Cryptococcus neoformans meningoencephalitis in HIV-seronegative patients".)
C. gattii is a basidiomycetous fungus, which can be found in the environment (see 'Environmental exposure' below). In clinical specimens, C. gattii is visualized as single or budding yeasts with round to cylindrical cells enveloped in a thick polysaccharide capsule. It was first proposed as a new taxonomic entity, Cryptococcus neoformans var gattii, in 1970 , in parallel with the characterization of the capsular antigens of C. neoformans. It is now characterized as a separate species, C. gattii.
Of the four major capsular serotypes of Cryptococcus spp (A, B, C, and D), B and C serotypes are exclusive to what has become known as C. gattii, a species distinct from C. neoformans [5,6]. Recognition of rare hybrids of C. gattii and C. neoformans provide evidence of taxonomic proximity, but not identity, between the two species .
Microbiologic tests used for the diagnosis of C. gattii infection are discussed separately. (See "Cryptococcus gattii infection: Clinical features and diagnosis", section on 'Culture and histopathology'.)
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