Cryptococcus neoformans
562589
223998062
2008-07-06T21:47:28Z
Ka Faraq Gatri
6892069
Category:Teliomycotina
{{Taxobox
| name = ''Cryptococcus neoformans''
| regnum = [[Fungi]]
| phylum = [[Basidiomycota]]
| subphylum = [[Basidiomycotina]]
| ordo = [[Sporidiales]]
| familia = [[Sporidiobolaceae]]
| genus = Filobasidiella (''[[Cryptococcus]]'')
| species = '''''Filobasidiella neoformans <br>(Cryptococcus neoformans)'''''
}}
'''''Cryptococcus neoformans''''' is an encapsulated yeast-like [[fungus]] that can live in both [[plant]]s and [[animal]]s.This species, also known by its [[teleomorph]] name, ''Filobasidiella neoformans'', belongs to the broad class of organisms called "club fungi" or [[Basidiomycota|Division Basidiomycota]], which is one the five major types of fungi. ''C. neoformans'' usually grows as a [[yeast]] (unicellular) and replicates by [[budding]]. Under certain conditions, both in nature and in the laboratory, ''C. neoformans'' can grow as a filamentous fungus as pictured here: [http://tolweb.org/tree/ToLimages/Filobasidiella_neoformans.jpg picture of the organism]<ref>[[Photomicrograph]] hosted by the [http://tolweb.org/tree/phylogeny.html Tree of Life project] and specifically contributed by the [http://www.dumru.mc.duke.edu/ Duke University Mycology Research Unit]; the picture is part of the [http://tolweb.org/tree?group=Hymenomycetes&contgroup=Basidiomycota Hymenomycetes article]. Retrieved 2005-03-15</ref>. When grown as a yeast, ''C. neoformans'' has a prominent capsule composed mostly of [[polysaccharides]]. Microscopically, the [[India ink]] stain is used for easy visualization of the capsule. The particles of ink pigment do not enter the capsule that surrounds the spherical yeast cell, resulting in a zone of clearance or "halo" around the cells.
[[Image:Cryptococcosis of lung in patient with AIDS. Mucicarmine stain 962 lores.jpg|thumb|right|250px|'''Cryptococcus neoformans''' seen in the lung of a patient with AIDS. The inner capsule of the organism stains red in this photomicrograph]]
The species ''C. neoformans'' is composed of three variants (v.): ''C. neoformans v. gattii'', ''v. grubii'', and ''v. neoformans''. ''C. neoformans v. gattii'' is found mostly in the [[tropics]], but has also been confirmed on southern [[Vancouver Island]] on the southwestern [[coast]] of [[Canada]]. ''Cryptococcus gattii'' has recently been shown to be different enough from other subspecies to be elevated to its own species level. ''C. neoformans v. grubii'' and ''v. neoformans'' have a worldwide distribution and are often found in soil which has been contaminated by bird excrement. The genome sequence of ''C. neoformans v. neoformans'' was published in 2005.<ref>{{cite journal | author=Loftus BJ, et al. | title=The genome of the basidiomycetous yeast and human pathogen Cryptococcus neoformans | journal=Science | volume=307 | issue=5713 | pages=1321–24 | pmid=15653466 | doi=10.1126/science.1103773 | year=2005 }}</ref> Recent studies made on [[Chernobyl Nuclear Power Plant]] have shown that colonies of ''Cryptococcus neoformans'' developed on the ruins of [[nuclear meltdown|melted down]] reactor harvest energy of [[particle radiation|radiation]] (primary [[beta radiation]] from [[caesium-137]]) itself.<ref>{{cite journal | author=Dadachova E, ''et al.'' | title=Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi | journal=PLoS One | volume=2(5)| doi=10.1371/journal.pone.0000457 | pmid=17520016 | year=2007 | pages=e457}}</ref>
Infection with ''C. neoformans'' is termed [[cryptococcosis]]. [[Meningitis]], especially as a secondary infection for [[AIDS]] patients, is often caused by ''C. neoformans''.
==Treatment==
Cryptococcosis that does not affect the central nervous system can be treated with [[fluconazole]] alone.
Cryptococcal meningitis should be treated for two weeks with [[intravenous]] [[Amphotericin B]] 0.7–1.0 (mg/kg)/day and oral [[flucytosine]] 100 (mg/kg)/day (or [[intravenous]] flucytosine 75 (mg/kg)/day if the patient is unable to swallow). This should then be followed by oral fluconazole 200mg daily for ten weeks<ref>{{cite journal | author=Saag MS, Graybill RJ, Larsen RA, ''et al.'' | title=Practice guidelines for the management of cryptococcal disease. Infectious Diseases Society of America |journal=Clin Infect Dis | year=2000 | volume=30 | issue=4 | pages=710–8 | pmid=10770733 | doi=10.1086/313757 }}</ref> and then 200 mg daily until the patient's [[CD4]] count is above 100 for three months and his HIV [[viral load]] is undetectable.<ref>{{cite journal | title=Discontinuation of secondary prophylaxis for cryptococcal meningitis in HIV-infected patients responding to highly active antiretroviral therapy
| journal=AIDS | volume=14 | issue=16 | year=2000 | pages=2615–26 | author=Martínez E, García-Viejo MA, Marcos MA, ''et al.''|pmid=11101078 | doi=10.1097/00002030-200011100-00029 }}</ref><ref>{{cite journal | title=Discontinuation of secondary prophylaxis for Cryptococcal meningitis in Human Immunodeficiency Virus-infected patients treated with highly active antiretroviral therapy: a prospective, multicenter, randomized study | author=Vibhagool A, Sungkanuparph S, Mootsikapun P, ''et al.'' | journal=Clin Infect Dis | volume=36 | year=2003 | pages=1329–31 |
doi=10.1086/374849 | pmid=12746781 }}</ref>
Intravenous [[Ambisome]] 4 (mg/kg)/day may be used but is not superior: its main use is in patients who do not tolerate Amphotericin B. The 200 (mg/kg)/day dose for flucytosine is not more effective, is associated with more side-effects and should not be used.
In Africa, oral fluconazole at a rate of 200 mg daily is used. However, this does not result in cure because it merely suppresses the fungus and does not kill it; viable fungus can continue to be grown from [[cerebrospinal fluid|CSF]] of patients who have taken fluconazole for many months. An increased dose of 400 mg daily does not improve outcomes,<ref>{{cite journal | title=Outcome of AIDS-associated cryptococcal meningitis initially treated with 200 mg/day or 400 mg/day of fluconazole | author=CF Schaars, Meintjes GA, Morroni C, ''et al.'' | journal=BMC Infect Dis | year=2006 | volume=6 | pages=118 | doi=10.1186/1471-2334-6-118 }}</ref> but preliminary data from [[Uganda]] shows that very high doses of 1200 mg or more per day may be effective. The duration of this treatment and the post-treatment maintenance dose is not known.
==References==
{{Reflist|2}}
==External links==
*[http://www.scq.ubc.ca/?p=525 A good overview of Cryptococcus neoformans biology from the Science Creative Quarterly]
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[[Category:Teliomycotina]]
[[Category:Yeasts]]