''Trichosporon asteroides'' is an asexual basidiomycetous fungus first described from human skin but now mainly isolated from

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

and

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

. ''T. asteroides'' is a

hyphal A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

fungus with a characteristically yeast-like appearance due to the presence of slimy

arthroconidia Arthroconidia are a type of fungal spore typically produced by segmentation of pre-existing fungal hyphae. Background These spores are asexual and are generally not as durable and environmentally persistent as, for instance, bacterial endospores o ...

. Infections by this species usually respond to treatment with

azole Azoles are a class of five-membered heterocyclic compounds containing a nitrogen atom and at least one other non-carbon atom (i.e. nitrogen, sulfur, or oxygen) as part of the ring. Their names originate from the Hantzsch–Widman nomenclature. Th ...

s and

amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis. Fo ...

History and taxonomy

''Trichosporon asteroides'' was isolated from lesion of male chin skin by Rinchin in

Bern german: Berner(in)french: Bernois(e) it, bernese , neighboring_municipalities = Bremgarten bei Bern, Frauenkappelen, Ittigen, Kirchlindach, Köniz, Mühleberg, Muri bei Bern, Neuenegg, Ostermundigen, Wohlen bei Bern, Zollikofen , website ...

in 1926 and named in the genus, ''Parendomyces''. ''T. asteroides'' was later reevaluated by Masao Ota and transferred to the genus ''

Trichosporon ''Trichosporon'' is a genus of anamorphic fungi in the family Trichosporonaceae. All species of ''Trichosporon'' are yeasts with no known teleomorphs (sexual states). Most are typically isolated from soil, but several species occur as a natural ...

'' as ''T. asteroides''. Ota noted that its

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e were more sparsely branched than other species in ''Trichosporon'', and it lacked the ability to ferment

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...

maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...

and

fructose Fructose, or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galacto ...

. Molecular phylogenetic study has since supported the placement of ''T. asteroides'' in the genus ''Trichsporon''. ''T. asteroides'' was determined to be conspecific with ''Fissuricella filamenta'' on the basis of DNA/DNA reassociation. Modern classifications support the placement of this species within the order

Trichosporonales The Trichosporonales are an order in the fungal class Tremellomycetes. The order contains two families and ten genera. Several species in the Trichosporonaceae The Trichosporonaceae are a family of fungi in the order Trichosporonales. The fam ...

Growth and morphology

''Trichosporon asteroides'' grows in a range of media including in the presence of the antifungal agent,

cycloheximide Cycloheximide is a naturally occurring fungicide produced by the bacterium ''Streptomyces griseus''. Cycloheximide exerts its effects by interfering with the translocation step in protein synthesis (movement of two tRNA molecules and mRNA in rela ...

. Colonies of ''T. asteroides'' grown on

Sabouraud agar Sabouraud agar or Sabouraud dextrose agar (SDA) is a type of agar growth medium containing peptones. It is used to cultivate dermatophytes and other types of fungi, and can also grow filamentous bacteria such as '' Nocardia''. It has utility f ...

appear white with a brain-like texture, reaching a diameter of 10 mm after 10 days growth at . Colonies have a radially furrowed outer zone and matt appearance that is not powdery like the related species, ''T. asahii''.

Antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

produced by infected patients can also be used to differentiate ''T. asahii'' and ''T. asteroides'' in disease. Weak growth is seen at but is absent at higher temperatures. ''T. asteroides'' can be distinguished from related ''Trichosporon'' species by its ability to utilize D-galactose,

L-rhamnose Rhamnose (Rha, Rham) is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose predominantly occurs in nature in its L-form as L-rhamnose (6-deoxy-L-mannose). This is unusual, since most o ...

erythritol Erythritol is an organic compound, a four-carbon sugar alcohol (or polyol) with no optical activity, used as a food additive and sugar substitute. It is naturally occurring. It can be made from corn using enzymes and fermentation. Its formula i ...

and

L-arabinitol Arabitol, or arabinitol, is a sugar alcohol. It can be formed by the reduction of either arabinose or lyxose. Some organic acid tests check for the presence of D-arabitol, which may indicate overgrowth of intestinal microbes such as ''Candida a ...

Physiology and pathogenesis

''Trichosporon asteroides'' does not ferment glucose, maltose, sucrose or fructose, a feature common to all ''Trichosporon'' species. ''T. asteroides'' causes

trichosporonosis Trichosporonosis is a systemic disease associated with fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. ...

, causing deep-seated, mucosa-associated, superficial, and systematic infections including blood. This species is one of the three most common ''Trichosporon'' species isolated in clinical settings. The fungus is sometimes recovered from specimens of

, and aspiration fluid,

vaginal mucosa In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen. ...

, male perigenital skin area, and

catheters In medicine, a catheter (/ˈkæθətər/) is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Cath ...

. The first record of this agent in a systemic infection involved a bloodstream infection. Main types of latent infection include

fungemia Fungemia is the presence of fungi or yeasts in the blood. The most common type, also known as candidemia, candedemia, or systemic candidiasis, is caused by '' Candida'' species; candidemia is also among the most common bloodstream infections of a ...

urinary tract infections A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...

peritonitis Peritonitis is inflammation of the localized or generalized peritoneum, the lining of the inner wall of the abdomen and cover of the abdominal organs. Symptoms may include severe pain, swelling of the abdomen, fever, or weight loss. One part or ...

endocarditis Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the ...

arthritis Arthritis is a term often used to mean any disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In som ...

esophagitis Esophagitis, also spelled oesophagitis, is a disease characterized by inflammation of the esophagus. The esophagus is a tube composed of a mucosal lining, and longitudinal and circular smooth muscle fibers. It connects the pharynx to the stomach; s ...

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...

brain abscess Brain abscess (or cerebral abscess) is an abscess caused by inflammation and collection of infected material, coming from local (ear infection, dental abscess, infection of paranasal sinuses, infection of the mastoid air cells of the temporal bone ...

splenic The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...

, and

uterine The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the hollow organ, organ in the female reproductive system, reproductive system of most female mammals, including humans that accommodates the embryonic development, embryonic an ...

infections. Allergies and systemic infections can also be caused by this fungus particularly in immunosuppressed people. Recently, ''T. asteroides'' was implicated in a case of kerion celsi, a rare, highly inflammatory scalp infection seen mainly in children. This fungus is rarely encountered in

zoonotic A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human (usually a vertebrate) to a human. ...

infections and has never been shown to cause disease in insects. However, ''T. asteroides'' was isolated from multifocal, irregularly raised skin lesions on a female Bottle-Nosed Dolphin, ''

Tursiops truncatus Bottlenose dolphins are Aquatic mammal, aquatic mammals in the genus ''Tursiops.'' They are common, cosmopolitan distribution, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. molecular biology, Molecular studies ...

'', in

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. In the absence of cultures and molecular biological analysis, the agent was initially suspected to be ''Paracoccidioides ceti'', a worldwide causative agent of

Paracoccidioidomycosis Paracoccidioidomycosis (PCM), also known as South American blastomycosis, is a fungal infection that can occur as a mouth and skin type, lymphangitic type, multi-organ involvement type (particularly lungs), or mixed type. If there are mouth ulcer ...

in dolphins.

Treatment

Azole antifungals are often used as a front-line therapy in

. Resistance to

amphotericin Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis. ...

flucytosine Flucytosine, also known as 5-fluorocytosine (5-FC), is an antifungal medication. It is specifically used, together with amphotericin B, for serious ''Candida'' infections and cryptococcosis. It may be used by itself or with other antifungals for ...

fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to prevent ...

, and

itraconazole Itraconazole, sometimes abbreviated ITZ, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, blastomycosis, coccidioidomycosis, histoplasmosis, and paracoccidioidomycosis. It may be given by mouth ...

have been described. Echinocandins, as a group, are ineffective against ''Trichosporon'' species.

Triazoles A triazole is a heterocyclic compound featuring a five-membered ring of two carbon atoms and three nitrogen atoms with molecular formula C2H3N3. Triazoles exhibit substantial isomerism, depending on the positioning of the nitrogen atoms within the ...

show better ''in vitro'' and ''in vivo'' antifungal activity than amphotericin B, while

voriconazole Voriconazole, sold under the brand name Vfend among others, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, candidiasis, coccidioidomycosis, histoplasmosis, penicilliosis, and infections by '' ...

also has excellent ''in vitro'' activity against ''Trichosporon asteroides''. Combination therapy regimens such as voriconazole and amphotericin B are also effective in serious infections.

Fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to prevent ...

has been used successfully in subcutaneous and deep infections.

References

{{Taxonbar, from=Q10703238 Tremellomycetes Fungi described in 1926 Fungal pathogens of humans Fungus species