UpToDate
Official reprint from UpToDate®
www.uptodate.com ©2016 UpToDate®

Microbiology and epidemiology of Cryptococcus neoformans infection

Authors
Gary M Cox, MD
John R Perfect, MD
Section Editor
Carol A Kauffman, MD
Deputy Editor
Jennifer Mitty, MD, MPH

INTRODUCTION

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 "Treatment of Cryptococcus neoformans 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".)

MICROBIOLOGY

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 [1]. 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 [2]. 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.

          

Subscribers log in here

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information or to purchase a personal subscription, click below on the option that best describes you:
Literature review current through: Nov 2016. | This topic last updated: Wed Jun 08 00:00:00 GMT+00:00 2016.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2016 UpToDate, Inc.
References
Top
  1. Franzot SP, Salkin IF, Casadevall A. Cryptococcus neoformans var. grubii: separate varietal status for Cryptococcus neoformans serotype A isolates. J Clin Microbiol 1999; 37:838.
  2. Hagen F, Khayhan K, Theelen B, et al. Recognition of seven species in the Cryptococcus gattii/Cryptococcus neoformans species complex. Fungal Genet Biol 2015; 78:16.
  3. Saul N, Krockenberger M, Carter D. Evidence of recombination in mixed-mating-type and alpha-only populations of Cryptococcus gattii sourced from single eucalyptus tree hollows. Eukaryot Cell 2008; 7:727.
  4. Firacative C, Trilles L, Meyer W. MALDI-TOF MS enables the rapid identification of the major molecular types within the Cryptococcus neoformans/C. gattii species complex. PLoS One 2012; 7:e37566.
  5. Eisenman HC, Casadevall A, McClelland EE. New insights on the pathogenesis of invasive Cryptococcus neoformans infection. Curr Infect Dis Rep 2007; 9:457.
  6. Kozel TR, Gotschlich EC. The capsule of cryptococcus neoformans passively inhibits phagocytosis of the yeast by macrophages. J Immunol 1982; 129:1675.
  7. Chang YC, Penoyer LA, Kwon-Chung KJ. The second capsule gene of cryptococcus neoformans, CAP64, is essential for virulence. Infect Immun 1996; 64:1977.
  8. Fries BC, Taborda CP, Serfass E, Casadevall A. Phenotypic switching of Cryptococcus neoformans occurs in vivo and influences the outcome of infection. J Clin Invest 2001; 108:1639.
  9. Salas SD, Bennett JE, Kwon-Chung KJ, et al. Effect of the laccase gene CNLAC1, on virulence of Cryptococcus neoformans. J Exp Med 1996; 184:377.
  10. Kwon-Chung KJ, Rhodes JC. Encapsulation and melanin formation as indicators of virulence in Cryptococcus neoformans. Infect Immun 1986; 51:218.
  11. Polacheck I, Platt Y, Aronovitch J. Catecholamines and virulence of Cryptococcus neoformans. Infect Immun 1990; 58:2919.
  12. Wang Y, Aisen P, Casadevall A. Cryptococcus neoformans melanin and virulence: mechanism of action. Infect Immun 1995; 63:3131.
  13. EMMONS CW. Saprophytic sources of Cryptococcus neoformans associated with the pigeon (Columba livia). Am J Hyg 1955; 62:227.
  14. Lazéra MS, Pires FD, Camillo-Coura L, et al. Natural habitat of Cryptococcus neoformans var. neoformans in decaying wood forming hollows in living trees. J Med Vet Mycol 1996; 34:127.
  15. Spec A, Raval K, Powderly WG. End-Stage Liver Disease Is a Strong Predictor of Early Mortality in Cryptococcosis. Open Forum Infect Dis 2016; 3:ofv197.
  16. Bernard C, Maucort-Boulch D, Varron L, et al. Cryptococcosis in sarcoidosis: cryptOsarc, a comparative study of 18 cases. QJM 2013; 106:523.
  17. Hajjeh RA, Brandt ME, Pinner RW. Emergence of cryptococcal disease: epidemiologic perspectives 100 years after its discovery. Epidemiol Rev 1995; 17:303.
  18. Kovacs JA, Kovacs AA, Polis M, et al. Cryptococcosis in the acquired immunodeficiency syndrome. Ann Intern Med 1985; 103:533.
  19. Powderly WG. Cryptococcal meningitis and AIDS. Clin Infect Dis 1993; 17:837.
  20. Mirza SA, Phelan M, Rimland D, et al. The changing epidemiology of cryptococcosis: an update from population-based active surveillance in 2 large metropolitan areas, 1992-2000. Clin Infect Dis 2003; 36:789.
  21. Park BJ, Wannemuehler KA, Marston BJ, et al. Estimation of the current global burden of cryptococcal meningitis among persons living with HIV/AIDS. AIDS 2009; 23:525.
  22. Rosen LB, Freeman AF, Yang LM, et al. Anti-GM-CSF autoantibodies in patients with cryptococcal meningitis. J Immunol 2013; 190:3959.
  23. Saijo T, Chen J, Chen SC, et al. Anti-granulocyte-macrophage colony-stimulating factor autoantibodies are a risk factor for central nervous system infection by Cryptococcus gattii in otherwise immunocompetent patients. MBio 2014; 5:e00912.
  24. Nosanchuk JD, Shoham S, Fries BC, et al. Evidence of zoonotic transmission of Cryptococcus neoformans from a pet cockatoo to an immunocompromised patient. Ann Intern Med 2000; 132:205.
  25. Kwon-Chung KJ, Bennett JE. Epidemiologic differences between the two varieties of Cryptococcus neoformans. Am J Epidemiol 1984; 120:123.