Cryptococcus gattii
Encyclopedia
Cryptococcus gattii, formerly known as Cryptococcus neoformans var gattii, is an encapsulated yeast
found primarily in tropical and subtropical climates. Its teleomorph is Filobasidiella bacillispora, a filamentous fungus
belonging to the class
Tremellomycetes
.
Cryptococcus gattii causes the human diseases of pulmonary cryptococcosis
(lung infection), basal meningitis
, and cerebral cryptococcomas. Occasionally, the fungus is associated with skin, soft tissue, lymph node
, bone, and joint infections. In recent years, it has appeared in British Columbia
, Canada
and the Pacific Northwest. It has been suggested that global warming
may have been a factor in its emergence in British Columbia. From 1999 through to early 2008, two hundred and sixteen people in British Columbia have been infected with C. gatti, and eight died from complications related to it. The fungus also infects animals, such as dog
s, koala
s and dolphin
s. In 2007, the fungus appeared for the first time in the United States
, in Whatcom County, Washington
and in April 2010 had spread to Oregon. The most recently identified strain, designated VGIIc, is particularly virulent, having proved fatal in 19 out of 218 known victims.
) and nervous system (causing meningitis and focal brain lesions called cryptococcomas) in humans. The main complication of lung infection is respiratory failure. Central nervous system infection may lead to hydrocephalus
, seizures and focal neurological deficit.
Unlike Cryptococcus neoformans
, C. gattii is not particularly associated with human immunodeficiency virus infection or other forms of immunosuppression. The fungus can cause disease in healthy people.
Molecular techniques may be used to speciate Cryptococcus from specimens that fail to culture.
Serum and CSF Cryptococcal antigen testing is a useful preliminary test for Cryptococcal infection, and has high sensitivity for disease. It does not distinguish between different species of Cryptococcus.
, either in its conventional or lipid formulation. The addition of oral or intravenous flucytosine
improves response rates. Oral fluconazole
is then administered for six months or more.
Antifungals alone are often insufficient to cure C. gattii infections, and surgery to resect infected lung (lobectomy
) or brain is often required. Ventricular
shunt
s and Ommaya reservoir
s are sometimes employed in the treatment of central nervous system
infection.
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
found primarily in tropical and subtropical climates. Its teleomorph is Filobasidiella bacillispora, a filamentous fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
belonging to the class
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Tremellomycetes
Tremellomycetes
The Tremellomycetes are a class of dimorphic fungi. Some species have a gelatinous fruiting body or a sacculate parenthesome. There are 3 orders, 11 families, 50 genera, and 377 species in the Tremellomycetes....
.
Cryptococcus gattii causes the human diseases of pulmonary cryptococcosis
Cryptococcosis
Cryptococcosis, or cryptococcal disease, is a potentially fatal fungal disease. It is caused by one of two species; Cryptococcus neoformans and Cryptococcus gattii. These were all previously thought to be subspecies of C...
(lung infection), basal meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, and cerebral cryptococcomas. Occasionally, the fungus is associated with skin, soft tissue, lymph node
Lymph node
A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...
, bone, and joint infections. In recent years, it has appeared in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and the Pacific Northwest. It has been suggested that global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
may have been a factor in its emergence in British Columbia. From 1999 through to early 2008, two hundred and sixteen people in British Columbia have been infected with C. gatti, and eight died from complications related to it. The fungus also infects animals, such as dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s, koala
Koala
The koala is an arboreal herbivorous marsupial native to Australia, and the only extant representative of the family Phascolarctidae....
s and dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s. In 2007, the fungus appeared for the first time in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, in Whatcom County, Washington
Whatcom County, Washington
Whatcom County is a county located in the U.S. state of Washington. Its name ultimately derives from the Lummi word Xwotʼqom, meaning "noisy water." As of 2010, the population was 201,140. The county seat is at Bellingham, which is also the county's largest city...
and in April 2010 had spread to Oregon. The most recently identified strain, designated VGIIc, is particularly virulent, having proved fatal in 19 out of 218 known victims.
Nomenclature
Cryptococcus gattii previously has had several different names including:- Cryptococcus neoformans var gattii
- Cryptococcus bacillisporus
Summary
Cryptococcal disease is a very rare disease that can affect the lungs (pneumoniaPneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
) and nervous system (causing meningitis and focal brain lesions called cryptococcomas) in humans. The main complication of lung infection is respiratory failure. Central nervous system infection may lead to hydrocephalus
Hydrocephalus
Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...
, seizures and focal neurological deficit.
Epidemiology
The highest incidences of C. gattii infections occur in Papua New Guinea and Northern Australia. Cases have also been reported in other regions, indicating its spread to India, Brazil, Vancouver Island in Canada, Washington State, and Oregon in the United States.Unlike Cryptococcus neoformans
Cryptococcus neoformans
Cryptococcus neoformans is an encapsulated yeast that can live in both plants and animals. Its teleomorph is Filobasidiella neoformans, a filamentous fungus belonging to the class Tremellomycetes. It is often found in pigeon excrement....
, C. gattii is not particularly associated with human immunodeficiency virus infection or other forms of immunosuppression. The fungus can cause disease in healthy people.
Transmission
The infection is caused by inhaling spores. The fungus is not transmitted from person to person or from animal to person. A person with cryptococcal disease is not contagious.Symptoms
Most people who are exposed to the fungus do not become ill. In people who become ill, symptoms appear many weeks to months after exposure. Symptoms of cryptococcal disease include:- Prolonged cough (lasting weeks or months)
- Sputum production
- Sharp chest pain
- Shortness of breath
- Sinusitis (cottony drainage, soreness, pressure)
- Severe headache (meningitis, encephalitis, meningoencephalitis)
- Stiff neck (prolonged and severe nuchal rigidity)
- Muscle soreness (mild to severe, local or diffuse)
- Photophobia (excessive sensitivity to light)
- Blurred or double vision
- Eye irritation ( soreness, redness)
- Focal neurological deficit
- Fever (delirium, hallucinations)
- Confusion (abnormal behavior changes, inappropriate mood swings)
- Seizures
- Dizziness
- Night sweatsSleep hyperhidrosisSleep hyperhidrosis, more commonly known as the night sweats, is the occurrence of excessive sweating during sleep. The sufferer may or may not also suffer from excessive perspiration while awake....
- Weight loss
- Nausea (with or without vomiting)
- Skin lesions (rashes, scaling, plaques, papules, nodules, blisters, subcutaneous tumors or ulcers)
- Lethargy
- Apathy
Diagnosis
Culture of sputum, bronchoalveolar lavage, lung biopsy, cerebrospinal fluid or brain biopsy specimens on selective agar allows differentiation between C. gattii and C. neoformans.Molecular techniques may be used to speciate Cryptococcus from specimens that fail to culture.
Serum and CSF Cryptococcal antigen testing is a useful preliminary test for Cryptococcal infection, and has high sensitivity for disease. It does not distinguish between different species of Cryptococcus.
Treatment
Medical treatment consists of prolonged intravenous therapy (for 6–8 weeks or longer) with the anti-fungal drug Amphotericin BAmphotericin B
Amphotericin B is a polyene antifungal drug, often used intravenously for systemic fungal infections...
, either in its conventional or lipid formulation. The addition of oral or intravenous flucytosine
Flucytosine
Flucytosine, or 5-fluorocytosine, a fluorinated pyrimidine analogue, is a synthetic antimycotic drug.It is structurally related to the cytostatic fluorouracil and to floxuridine. It is available in oral and in some countries also in injectable form. A common brand name is Ancobon. Flucytosine was...
improves response rates. Oral fluconazole
Fluconazole
Fluconazole is a triazole antifungal drug used in the treatment and prevention of superficial and systemic fungal infections. In a bulk powder form, it appears as a white crystalline powder, and it is very slightly soluble in water and soluble in alcohol. It is commonly marketed under the trade...
is then administered for six months or more.
Antifungals alone are often insufficient to cure C. gattii infections, and surgery to resect infected lung (lobectomy
Lobectomy
Lobectomy means surgical excision of a lobe. This may refer to a lobe of the lung, a lobe of the thyroid , or a lobe of the brain ....
) or brain is often required. Ventricular
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
shunt
Shunt (medical)
In medicine, a shunt is a hole or a small passage which moves, or allows movement of fluid from one part of the body to another. The term may describe either congenital or acquired shunts; and acquired shunts may be either biological or mechanical.* Cardiac shunts may be described as...
s and Ommaya reservoir
Ommaya reservoir
An Ommaya reservoir is an intraventricular catheter system that can be used for the aspiration of cerebrospinal fluid or for the delivery of drugs into the cerebrospinal fluid. It consists of a catheter in one lateral ventricle attached to a reservoir implanted under the scalp...
s are sometimes employed in the treatment of central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
infection.
See also
- Jenney A, Pandithage K, Fisher DA and Currie BJ. Cryptococcus infection in Tropical Australia. Journal of Clinical Microbiology 2004; 42(8): 3865-3868.