Microbiology and epidemiology of Cryptococcus neoformans infection
- Gary M Cox, MD
Gary M Cox, MD
- Professor of Medicine
- Duke University Medical Center
- John R Perfect, MD
John R Perfect, MD
- Professor of Medicine
- Duke University Medical Center
Cryptococcosis is an invasive fungal infection due to Cryptococcus neoformans or Cryptococcus gattii that has become increasingly prevalent in immunocompromised patients.
The microbiology and epidemiology of Cryptococcus species and cryptococcosis will be reviewed here, with an emphasis on C. neoformans. The microbiology and epidemiology of C. gattii is discussed in detail elsewhere. The clinical features, diagnosis, and management of C. neoformans infections are also discussed separately. (See "Cryptococcus gattii infection: Microbiology, epidemiology, and pathogenesis" 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" and "Cryptococcus neoformans: Treatment of meningoencephalitis and disseminated infection in HIV seronegative patients" and "Treatment of Cryptococcus neoformans meningoencephalitis in HIV-infected patients" and "Cryptococcus neoformans infection outside the central nervous system" and "Clinical management and monitoring during antifungal therapy of the HIV-infected patient with cryptococcal meningoencephalitis".)
Taxonomy — C. neoformans and C. gattii are basidiomycetous, encapsulated yeasts. C. neoformans and C. gattii can be subclassified into four serotypes and two species with two varieties. The serotypes are based upon capsular agglutination reactions and are designated A, B, C, or D.
Serotype A and D cryptococci were previously classified under the species neoformans. However, it has been proposed that the serotype A cryptococci be considered as a separate variety based upon genotypic differences . Serotype A cryptococci are now considered the variety grubii and are divided into three molecular subtypes: VNI, VNII, and VNB. Serotype D are classified under the variety neoformans. Serotypes B and C are now considered as a separate species called C. gattii . A detailed discussion of C. gattii is found elsewhere. (See "Cryptococcus gattii infection: Microbiology, epidemiology, and pathogenesis", section on 'Molecular types'.)
Life cycle — The life cycle of C. neoformans involves asexual and sexual forms. The asexual form exists as yeast and reproduces by budding. These haploid, unicellular yeasts are the only forms of C. neoformans and C. gattii that have been recovered from human infections.
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