Exophiala phaeomuriformis

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Exophiala phaeomuriformis
Exophiala phaeomuriformis.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Eurotiomycetes
Order: Chaetothyriales
Family: Herpotrichiellaceae
Genus: Exophiala
Species:
E. phaeomuriformis
Binomial name
Exophiala phaeomuriformis
Matos (2003)
Synonyms
  • Sarcinomyces phaeomuriformisT. Matsumoto (1986)

Exophiala phaeomuriformis is thermophilic fungus belonging to the genus Exophiala and the family Herpotrichiellaceae. [1] [2] it is a member of the group of fungi known as black yeasts, and is typically found in hot and humid locations, such as saunas, bathrooms, and dishwashers. [3] This species can cause skin infections [4] and is typically classified as a Biosafety Risk Group 2 agent. [5]

Contents

History

Exophiala phaeomuriformis is a member of the genus Exophiala, described in 1952 based on E. jeanselmei. [1] Thirty species of Exophiala are currently recognized [6] amongst which Exophiala (Wangiella) dermatitidis is the most common. [7] When studying samples of E. dermatitidis, Tadahiko Matsumoto and colleagues observed strains with a granular colonial form and distinctive microscopic morphology. [8] Based on the resemblance of these strains to the genus Sarcinomyces, they proposed the new name, S. phaeomuriformis. [8] This taxon was transferred to the genus Exophiala by Tiago Matos and co-workers in 2003 because of its yeast-like morphology (rather than the meristematic form characteristic to members of the genus Sarcinomyces), and its closer DNA homology to the genus Exophiala. [9]

Exophiala phaeomuriformis is a dematiceous (darkly pigmented) fungus and member of the group of fungi known as the black yeasts. [10] [11] Black yeasts are an unrelated category of fungi that share yeast-like morphology and possess darkly melanized cell walls. [5] Although their DNA sequences are distinctive, E. phaeomuriformis and E. dermatitidis are so closely related that the two cannot be reliably differentiated morphologically or physiologically. [5] [12] Antigenic cross-reactivity suggests that E. phaeomuriformis may have originated as multicellular variant of E. dematitidis. [10]

Growth and morphology

Like many other black yeasts, Exophiala phaeomuriformis is known only by its asexual form and no sexual form has been found. [4] [5] [8] It is a thermophilic fungus preferring temperatures between 37–42 °C (99–108 °F) [2] but growing at any temperature between 15–42 °C (59–108 °F). [3] Exophilala phaeomuriformis is more sensitive than other black yeasts to salt, incapable of growth at concentrations of sodium chloride exceeding 17%. [3] Like other members of the genus Exophiala, it is able to tolerate a wide range of pH (2.5–12.5). [3]

Colonies of E. phaeomuriformis are hyaline, mycoid, and smooth when young [9] but become black, dry, crumbly, raised, and mulberry-like in texture with age. [4] [8] Some strains fail to undergo this morphological switch and remain yeast-like in age. [5] [8] By contrast, many strains of E. dermatitidis become mycelial with age. [8] Hyphal growth has not been observed in E. phaeomuriformis. [8] Instead, colonies develop from loosely packed, single, and rounded budding yeast cells that are either scattered or aggregated in groups. [5] [8] Vegetative cells can either by unicellular or muriform (septate in all planes) or become divided by transverse septa only. [4] [8] Yeast cells are thick-walled and spherical or near-spherical in shape. [4] [5] Budding cells can have broad bases, occur in chains, and be multilateral, budding in different directions. [9]

Physiology

Like other member of the genus Exophiala, E. phaeomuriformis is saprotrophic, obtaining its energy exclusively from non-living organic materials. [6] When inoculated on a suitable growth medium under optimal conditions, the growth of E. phaeomuriformis is initiated in roughly 3 days; [3] however, when subject to competition, the cells may remain in a stationary state for many weeks prior to the development of visible growth. [3] Similar to E. dematitidis, E. phaeomuriformis is unable to assimilate nitrate, nitrite and melibiose; however it differs in it that some strains are unable to metabolize D-gluconate, D-glucuronate, D-galacturonate and glucono-δ-lactone. [10]

Habitat and ecology

Exophiala phaeomuriformis has a proclivity for environments rich in mono- and polyaromatic compounds, such as hydrocarbons, where it uses these compounds as sources of energy. [3] The species is plurivorous, occurring on a wide range of materials from contaminated soils and toluene rich environments to wild berries and animal feces. [3] It is also found in environments containing the preservative creosote, such as railroad ties where it is an important agent of biodeterioration. [3] [13] In indoor environments, E. phaeomuriformis occurs in warm and moist environments such as toilets, saunas, or dishwashers. [2] This species is found world-wide. [14]

Human disease

Exophiala phaeomuriformis is a rare causative agent of phaeohyphomycosis [15] in cutaneous, subcutaneous and deep tissues, [4] and is responsible for 6.4% of infections caused by black yeasts. [7] Infection usually occurs following skin abrasion or penetrating injuries. [11] Exophiala phaeomuriformis can also cause corneal infection following eye exposure to contaminated water. [1] People with cystic fibrosis (CF) are considered abnormally susceptible to Exophiala infections, including E. phaeomuriformis. [14] [16] It has been suggested that differences in the microbiota profiles of CF patients may be responsible for this predisposition. [17] Treatment of E. phaeomuriformis involves a combination of surgical debridement and antifungal therapy. [15] A range of antifungal agents including caspofungin, voriconazole, itraconazole, posaconazole, and amphotericin B are active against this species. [16] [18] Due to its pathogenic potential, E. phaeomuriformis is regarded as a Biosafety Risk Group 2 agent in the laboratory. [5]

Related Research Articles

<i>Exophiala</i> Genus of fungi

Exophiala is a genus of anamorphic fungi in the family Herpotrichiellaceae. The widespread genus contains 28 species. The genus was formally described by J. W. Carmichael in 1966.

Exophiala jeanselmei is a saprotrophic fungus in the family Herpotrichiellaceae. Four varieties have been discovered: Exophiala jeanselmei var. heteromorpha, E. jeanselmei var. lecanii-corni, E. jeanselmei var. jeanselmei, and E. jeanselmei var. castellanii. Other species in the genus Exophiala such as E. dermatitidis and E. spinifera have been reported to have similar annellidic conidiogenesis and may therefore be difficult to differentiate.

<i>Blastomyces dermatitidis</i> Species of fungus

Blastomyces dermatitidis is a dimorphic fungus that causes blastomycosis, an invasive and often serious fungal infection found occasionally in humans and other animals. It lives in soil and wet, decaying wood, often in an area close to a waterway such as a lake, river or stream. Indoor growth may also occur, for example, in accumulated debris in damp sheds or shacks. The fungus is endemic to parts of eastern North America, particularly boreal northern Ontario, southeastern Manitoba, Quebec south of the St. Lawrence River, parts of the U.S. Appalachian mountains and interconnected eastern mountain chains, the west bank of Lake Michigan, the state of Wisconsin, and the entire Mississippi Valley including the valleys of some major tributaries such as the Ohio River. In addition, it occurs rarely in Africa both north and south of the Sahara Desert, as well as in the Arabian Peninsula and the Indian subcontinent. Though it has never been directly observed growing in nature, it is thought to grow there as a cottony white mold, similar to the growth seen in artificial culture at 25 °C (77 °F). In an infected human or animal, however, it converts in growth form and becomes a large-celled budding yeast. Blastomycosis is generally readily treatable with systemic antifungal drugs once it is correctly diagnosed; however, delayed diagnosis is very common except in highly endemic areas.

<i>Pseudallescheria boydii</i> Species of fungus

Pseudallescheria boydii is a species of fungus classified in the Ascomycota. It is associated with some forms of eumycetoma/maduromycosis and is the causative agent of pseudallescheriasis. Typically found in stagnant and polluted water, it has been implicated in the infection of immunocompromised and near-drowned pneumonia patients. Treatment of infections with P. boydii is complicated by resistance to many of the standard antifungal agents normally used to treat infections by filamentous fungi.

<i>Lomentospora prolificans</i> Species of fungus

Lomentospora prolificans is an emerging opportunistic fungal pathogen that causes a wide variety of infections in immunologically normal and immunosuppressed people and animals. It is resistant to most antifungal drugs and infections are often fatal. Drugs targeting the Class II dihydroorotate dehydrogenase (DHODH) proteins of L. prolificans, Scedosporium, Aspergillus and other deadly moulds are the basis for at least one new therapy, Olorofim, which is currently in phase 2b clinical trials and has received breakthrough status by FDA. For information on all DHODH proteins, please see Dihydroorotate dehydrogenase.

<i>Fonsecaea pedrosoi</i> Species of fungus

Fonsecaea pedrosoi is a fungal species in the family Herpotrichiellaceae, and the major causative agent of chromoblastomycosis. This species is commonly found in tropical and sub-tropical regions, especially in South America, where it grows as a soil saprotroph. Farming activities in the endemic zone are a risk factor for the development of chromoblastomycosis.

<i>Trichophyton mentagrophytes</i> Species of fungus

Trichophyton mentagrophytes is a species in the fungal genus Trichophyton. It is one of three common fungi which cause ringworm in companion animals. It is also the second-most commonly isolated fungus causing tinea infections in humans, and the most common or one of the most common fungi that cause zoonotic skin disease. Trichophyton mentagrophytes is being frequently isolated from dogs, cats, rabbits, guinea pigs and other rodents, though at least some genetic variants possess the potential of human-to-human transmission, e.g. Type VII and Type VIII. Particular genetic variants of the fungus have distinct geographic ranges.

<i>Microsporum canis</i> Species of fungus

Microsporum canis is a pathogenic, asexual fungus in the phylum Ascomycota that infects the upper, dead layers of skin on domesticated cats, and occasionally dogs and humans. The species has a worldwide distribution.

<i>Exophiala dermatitidis</i> Species of fungus

Exophiala dermatitidis is a thermophilic black yeast, and a member of the Herpotrichiellaceae. While the species is only found at low abundance in nature, metabolically active strains are commonly isolated in saunas, steam baths, and dish washers. Exophiala dermatitidis only rarely causes infection in humans, however cases have been reported around the world. In East Asia, the species has caused lethal brain infections in young and otherwise healthy individuals. The fungus has been known to cause cutaneous and subcutaneous phaeohyphomycosis, and as a lung colonist in people with cystic fibrosis in Europe. In 2002, an outbreak of systemic E. dermatitidis infection occurred in women who had received contaminated steroid injections at North Carolina hospitals.

Black yeasts, sometimes also black fungi, dematiaceous fungi, microcolonial fungi or meristematic fungi is a diverse group of slow-growing microfungi which reproduce mostly asexually. Only few genera reproduce by budding cells, while in others hyphal or meristematic (isodiametric) reproduction is preponderant. Black yeasts share some distinctive characteristics, in particular a dark colouration (melanisation) of their cell wall. Morphological plasticity, incrustation of the cell wall with melanins and presence of other protective substances like carotenoids and mycosporines represent passive physiological adaptations which enable black fungi to be highly resistant against environmental stresses. The term "polyextremotolerance" has been introduced to describe this phenotype, an example of which is the species Aureobasidium pullulans. Presence of 1,8-dihydroxynaphthalene melanin in the cell wall confers to the microfungi their characteristic olivaceous to dark brown/black colour.

<i>Cladophialophora bantiana</i> Species of fungus

Cladophialophora bantiana is a melanin producing mold known to cause brain abscesses in humans. It is one of the most common causes of systemic phaeohyphomycosis in mammals. Cladophialophora bantiana is a member of the ascomycota and has been isolated from soil samples from around the world.

Malassezia pachydermatis is a zoophilic yeast in the division Basidiomycota. It was first isolated in 1925 by Fred Weidman, and it was named pachydermatis after the original sample taken from an Indian rhinoceros with severe exfoliative dermatitis. Within the genus Malassezia, M. pachydermatis is most closely related to the species M. furfur. A commensal fungus, it can be found within the microflora of healthy mammals such as humans, cats and dogs, However, it is capable of acting as an opportunistic pathogen under special circumstances and has been seen to cause skin and ear infections, most often occurring in canines.

Phaeohyphomycosis is a diverse group of fungal infections, caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these. It can be associated an array of melanistic filamentous fungi including Alternaria species,Exophiala jeanselmei, and Rhinocladiella mackenziei.

Scedosporiosis is the general name for any mycosis - i.e., fungal infection - caused by a fungus from the genus Scedosporium. Current population-based studies suggest Scedosporium prolificans and Scedosporium apiospermum to be among the most common infecting agents from the genus, although infections caused by other members thereof are not unheard of. The latter is an asexual form (anamorph) of another fungus, Pseudallescheria boydii. The former is a “black yeast”, currently not characterized as well, although both of them have been described as saprophytes.

<i>Fonsecaea compacta</i> Species of fungus

Fonsecaea compacta is a saprophytic fungal species found in the family Herpotrichiellaceae. It is a rare etiological agent of chromoblastomycosis, with low rates of correspondence observed from reports. The main active components of F. compacta are glycolipids, yet very little is known about its composition. F. compacta is widely regarded as a dysplastic variety of Fonsecaea pedrosoi, its morphological precursor. The genus Fonsecaea presently contains two species, F. pedrosoi and F. compacta. Over 100 strains of F. pedrosoi have been isolated but only two of F. compacta.

<i>Rhinocladiella mackenziei</i> Species of fungus

Rhinocladiella mackenziei is a deeply pigmented mold that is a common cause of human cerebral phaeohyphomycosis. Rhinocladiella mackenziei was believed to be endemic solely to the Middle East, due to the first cases of infection being limited to the region. However, cases of R. mackenziei infection are increasingly reported from regions outside the Middle East. This pathogen is unique in that the majority of cases have been reported from immunologically normal people.

<i>Cladophialophora carrionii</i> Species of fungus

Cladophialophora carrionii is a melanized fungus in the genus Cladophialophora that is associated with decaying plant material like cacti and wood. It is one of the most frequent species of Cladophialophora implicated in human disease. Cladophialophora carrionii is a causative agent of chromoblastomycosis, a subcutaneous infection that occurs in sub-tropical areas such as Madagascar, Australia and northwestern Venezuela. Transmission occurs through traumatic implantation of plant material colonized by C. carrionii, mainly infecting rural workers. When C. carrionii infects its host, it transforms from a mycelial state to a muriform state to better tolerate the extreme conditions in the host's body.

Exophiala pisciphila is a mesophilic black yeast and member of the dark septate endophytes. This saprotrophic fungus is found commonly in marine and soil environments. It is abundant in harsh environments like soil contaminated with heavy metals. E. pisciphila forms symbiotic relationships with various plants by colonizing on roots, conferring resistance to drought and heavy metal stress. It is an opportunistic pathogen that commonly causes infections in captive fish and amphibians, while rarely causing disease in humans. Secondary metabolites produced by this species have potential clinical antibiotic and antiretroviral applications.

Cladophialophora arxii is a black yeast shaped dematiaceous fungus that is able to cause serious phaeohyphomycotic infections. C. arxii was first discovered in 1995 in Germany from a 22-year-old female patient suffering multiple granulomatous tracheal tumours. It is a clinical strain that is typically found in humans and is also capable of acting as an opportunistic fungus of other vertebrates Human cases caused by C. arxii have been reported from all parts of the world such as Germany and Australia.

Capronia mansonii is a mesophilic black yeast that is a part of the Herpotrichiellaceae. The species is uncommon in nature but is saprotrophic in nature and been discovered on decaying plant matter, particularly wood. This fungus is naturally found in the Netherlands and has successfully been cultured in lab. It is a teleomorph of the ascomycota division and possesses brown spores.

References

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  12. ↑ Haase, G.; Sonntag, L.; van de Peer, Y.; Uijthof, J. M. J.; Podbielski, A.; Melzer-Krick, B. (March 1995). "Phylogenetic analysis of ten black yeast species using nuclear small subunit rRNA gene sequences". Antonie van Leeuwenhoek. 68 (1): 19–33. doi:10.1007/BF00873289. PMID   8526477. S2CID   2819521.
  13. ↑ K June; Wang (1990). Identification manual for fungi from utility poles in the eastern United States. Rockville, Md.: American Type Culture Collection. pp.  356. ISBN   9780930009311.
  14. 1 2 Döğen, Aylin; Ilkit, Macit; de Hoog, G. Sybren (October 2013). "Black yeast habitat choices and species spectrum on high altitude creosote-treated railway ties". Fungal Biology. 117 (10): 692–696. doi:10.1016/j.funbio.2013.07.006. PMID   24119407.
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  17. ↑ Lebecque, Patrick; Leonard, Anissa; Huang, Daniel; Reychler, Grégory; Boeras, Anca; Leal, Teresinha; Symoens, Françoise (November 2010). "Exophiala (Wangiella) dermatitidis and cystic fibrosis – Prevalence and risk factors". Medical Mycology. 48 (O1): S4–S9. doi: 10.3109/13693786.2010.495731 . PMID   21067329.
  18. ↑ Rivard, Robert G.; McCall, Suzanne; Griffith, Matthew E.; Hawley, Joshua S.; Ressner, Roseanne A.; Borra, Himabindu; Moon, James E.; Beckius, Miriam L.; Murray, Clinton K.; Hospenthal, Duane R. (January 2007). "Efficacy of caspofungin and posaconazole in a murine model of disseminated infection". Medical Mycology. 45 (8): 685–689. doi: 10.1080/13693780701390157 . PMID   17885951.
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