Cryptococcus

Not to be confused with Cryptosporidium.

Cryptococcus
Cryptococcus neoformans
Scientific classification
Kingdom:	Fungi
Phylum:	Basidiomycota
Class:	Tremellomycetes
Order:	Tremellales
Family:	Tremellaceae
Genus:	Cryptococcus Vuill.
Type species
Cryptococcus neoformans
Synonyms
Filobasidiella

Cryptococcus (literally "hidden sphere") is a genus of fungus. Species grow in culture as yeasts. The perfect (sexual) forms or teleomorphs of Cryptococcus species are filamentous fungi in the genus Filobasidiella. The name Cryptococcus is used when referring to the imperfect forms (yeast states) of the fungi.

Cryptococcus neoformans is the most prominent medically important species. It is best known for causing a severe form of meningitis and meningo-encephalitis in people with HIV/AIDS. There are about 37 recognized species of Cryptococcus, but the taxonomy of the group is currently being re-evaluated with up-to-date methods. The majority of species live in the soil and are not harmful to humans. Very common species include Cryptococcus laurentii and Cryptococcus albidus. Of all species, Cryptococcus neoformans is the major human and animal pathogen. However, Cryptococcus laurentii and Cryptococcus albidus have been known to occasionally cause moderate-to-severe disease in human patients with compromised immunity (owing to HIV infection, cancer chemotherapy, metabolic immunosuppression, et cetera).^[1][2]

Field stain showing Cryptococcus species in lung tissue

Cryptococcus gattii (formerly Cryptococcus neoformans var gattii) is endemic to tropical parts of the continent of Africa and Australia. It is capable of causing disease (cryptococcosis) in non-immunocompromised people. It has been isolated from eucalyptus trees in Australia. Since 1999, there has been an outbreak of Cryptococcus gattii infections in eastern Vancouver Island,^[3] an area not generally thought to be endemic for this organism. Cases have since been described in the Pacific Northwest, in both Canada and the United States.^[4]

The cells of these species are covered in a thin layer of glycoprotein capsular material that has a gelatin-like consistency and that, among other functions, serves to help extract nutrients from the soil. But C. neoformans capsule is different in being richer in glucuronic acid and mannose, having O-acetyl groups,^[5] and functioning as the major virulence factor in cryptococcal infection and disease.^[6]

References

1. ^ Cheng MF, Chiou CC, Liu YC, Wang HZ, Hsieh KS (2001) Cryptococcus laurentii fungemia in a premature neonate. Journal of Clinical Microbiology. 39(4):1608–11. A good review of C. laurentii cases till year 2000.
2. ^ Results from a PubMed Search on terms: "Cryptococcus albidus Infection" – list of references for C. albidus clinical infections.
3. ^ Lindberg J, Hagen F, Laursen A, et al. (2007). "Cryptococcus gattii Risk for Tourists Visiting Vancouver Island, Canada". Emerg Infect Dis 13 (1): 178–79. doi:10.3201/eid1301.060945. PMC 2725802. PMID 17370544. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2725802. 
4. ^ MacDougall L, Kidd SE, Galanis E, et al. (2007). "Spread of Cryptococcus gattii in British Columbia, Canada, and Detection in the Pacific Northwest, USA". Emerg Infect Dis 13 (1): 42–50. doi:10.3201/eid1301.060827. PMC 2725832. PMID 17370514. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2725832. 
5. ^ Ross A, Taylor IE (1981) Extracellular glycoprotein from virulent and avirulent Cryptococcus species. Infection and Immunity. 31(3):911–8
6. ^ Casadevall A and Perfect JR (1998) Cryptococcus neoformans. American Society for Microbiolgy, ASM Press, Washington DC, 1st edition.