Cryptococcus neoformans

Cryptococcosis: Description, Causes and Risk Factors:Cryptococcosis is a systemic fungal infection widely distributed throughout the world, produced by Cryptococcus neoformans (C. Neoformans) whose reservoir is the faeces of poultry (especially pigeons) as well as and soils contaminated by fruit.C. neoformans grows naturally in the environment. C. neoformans var neoformans is ubiquitous in the soil, where it grows as a saprophyte (an organism that feeds on dead organic matter especially a fungus or bacterium). It is common in old pigeon nests and around pigeon droppings; the bird droppings appear to create a favorable environment for its growth. It can also be isolated from numerous environmental sources including vegetables and fruit, house dust, air conditioners, air and sawdust. It can survive for months to years outside the host.C. neoformans var gattii is found in bark and plant debris under eucalyptus trees (the river red gum tree Eucalyptus camaldulensis and the forest red gum tree, E. tereticornis). It is also found in the air around these trees, particularly when they bloom in late spring. It is not associated with pigeon droppings. Recently, C. neoformans var gattii was isolated from trees and soil on Vancouver Island in British Columbia.The route of entry is usually by inhalation and from the lung spread to other organs, but rarely penetrates the skin and mucosas with previous injuries. Once spread is lethal if not treated properly.Transmission seems to be mainly by inhalation, but C. neoformans can also enter the body through the skin. Infections seem to be acquired mainly from the environment. Cryptococcosis can also result from the reactivation of a latent infection.Risk Factors:Diabetes mellitus.
  • Hepatic cirrhosis.
  • Haematological malignancies.
  • Sarcoidosis.
  • Connective tissue disorders.
  • Corticosteroid therapy.
  • Novel immunosuppressive monoclonal antibody therapies.
Symptoms:CryptococcosisSymptoms may include:Bone pain or tenderness of the breastbone (sternum).
  • Blurred vision or double vision (diplopia).
  • Chest pain.
  • Confusion.
  • Cough - dry.
  • Fatigue.
  • Fever.
  • Headache.
  • Nausea.
  • Skin rash, including pinpoint red spots (petechiae), ulcers, or other skin lesions.
  • Sweating -- unusual, excessive at night.
  • Swollen glands.
  • Unintentional weight loss.
Diagnosis:Cryptococcosis is usually diagnosed by detecting C.neoformans in biopsies, impression smears, aspirates, orswabs of nasal secretions or skin exudates. In cases of CNSdisease, C. neoformans may be found in the cerebrospinalfluid (CSF).C. neoformans can sometimes be found in clinical samples by direct observation. This organism is an encapsulated4 to 6 mm, round to oval yeast. It is surrounded by a halo-likecapsule that stains strongly with Mayer's mucicarmine. Inan India ink preparation, yeast cells surrounded by a clearhalo (the capsule) may be seen; unless budding is observed,the organisms can be confused with fat droplets or otherartifacts.Other useful stains include Alcian blue, Gomorimethenamine silver, periodic acid-Schiff (PAS), Masson-Fontan silver stain, Gram's stain, new methylene blue andWright's stain. C. neoformans can be identified in the tissuesby immunofluorescence (a technique that uses antibodies linked to a fluorescent dye in order to study antigens in a sample of tissue).A definitive diagnosis can be obtained by culture.Although C. neoformans grows on most media, growth isbest on fungal media such as Sabaraud's dextrose agar without cycloheximide. Colonies usually appear within 2-5 daysbut growth may be delayed in samples with few organisms.The organism is identified by its appearance, its ability togrow at 37°C and biochemical tests.A latex agglutination test or ELISA can detect C. neoformans capsular antigens in blood, CSF or urine.Serology may be useful in some cases; however, largeamounts of capsular antigen in the circulation appear to tieup antibodies.Treatment:Cryptococcosis can be treated with amphotericin B, flucytosine, itraconazole and fluconazole. Amphotericin B and flucytosine are often used in combination. A combination of ketoconazole and itraconazole has been effective in some experimentally infected cats, including animals with neurologic disease. In most cases, there is no practical means of prevention other than to avoid exposure to the soil, particularly soil contaminated with abundant bird droppings, and the environment around eucalyptus trees.NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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