| Scytalidium hyalinum | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Leotiomycetes |
| Order: | Helotiales |
| Genus: | Scytalidium |
| Species: | S. hyalinum |
| Binomial name | |
| Scytalidium hyalinum C.K. Campb. & J.L. Mulder | |
Scytalidium hyalinum is an ascomycete fungus currently in the genus Scytalidium . It causes dermatomycosis and systemic infections in humans and it is widespread throughout the world.
Scytalidium hyalinum was first isolated in 1977 in England by C.K. Campbell. [1] It was isolated from 8 immigrants from Jamaica, Nigeria, and Sierra Leone who had shown signs of tinea pedis and skin infections. [1]
It is unclear whether S. hyalinum and Neoscytalidium dimidiatum are very closely related or if S. hyalinum is a same species mutation of N. dimidiatum. Comparisons of several N. dimidiatum and S. hyalinum strains have found that all S. hyalinum strains differed from the N. dimidiatum strains by a single A-G polymorphism at position 144 and by the absence of an IE intron group that is present in N. dimidatum, [2] [3] which suggests they are different species.
Colonies on malt agar grow rapidly at 27 °C (81 °F) and produce white fluffy superficial mycelia as well as immersed mycelia. [1] Hyphae are up to 4 μm in width, pale or colorless, septate, and smooth. Stromata are absent. Conidiophores are unusually small (micronematous), can be branched or unbranched, pale or colorless, straight, smooth, and irregular. Conidia are arthrosporic, simple, cylindrical to ellipsoid or rounded, sometimes rough, catenulate, separating, hyaline or pale, with thin cell walls. [1]
Colonies are visible after only a few days of growth on Sabouraud’s dextrose agar. [4] Fungal growth is robust at 37 °C (99 °F), the temperature of the human body. [5] Growth is poor above 40 °C (104 °F), but colonies can survive at 42 °C (108 °F) for two weeks. [5]
Scytalidium hyalinum is able to hydrolyse gelatin, casein, tyrosine, olive oil, and urea. [5]
It is most likely endemic to West Africa, [1] [6] the West Indies, [1] and the Pacific. [7] It is also present in the UK, [1] Spain, [6] Italy, [8] Australia, [9] and France [10] via travel and immigration. Until 2007, when it was recovered from soil in Indian rat burrows in India, S. hyalinum had never been isolated from the environment. [7] [11]
Infection resembles N. dimidiatum infections. Lesions are confined to hands, feet, and toenails. [4] The fungus is found in the toewebs and nails. Nail changes involve thickening, yellow-brown discoloration, and subungual keratosis. It can cause distinctive thickening, lichenification, and discoloration of the knuckles and sides of fingers, but it is not consistent. [4] More than half of patients reported itching at site of infection. [7] Infections are usually chronic, which suggests that the immune response is ineffective or deficient. [12] [7]
Scytalidium hyalinum can present a mixed infection with N. dimidiatum. [1] [4] The infections of both S. hyalinum and N. dimidiatum are virtually clinically indistinguishable from the chronic, non-inflammatory dry type of Trichophyton rubrum infection. [7]
Both S. hyalinum and N. dimidiatum are resistant to treatment by griseofulvin and susceptible to cycloheximide. [1] It is sensitive to clotrimazole and miconazole in vitro. [4] Cases have also been treated with oral itraconazole. [8] An in vitro study suggested that voriconazole could be effective for refractory infections. [13] S. hyalinum is more susceptible to voriconazole than N. dimidiatum, perhaps because of its lack of protective melanin. [13]
Scytalidium hyalinum and N. dimidiatum share a very similar antigenic structure distinct from other pathogenic fungi. [7] The two species also demonstrate cross-reactivity with each other’s antigens and anti-sera derived from patients. [7] Cross-reactivity between N. dimidiatum and S. hyalinum exoantigens has been demonstrated in both immunodiffusion tests and fused rocket immunoelectrophoresis tests. [7]
In 2018, the first case of ocular infection by S. hyalinum was documented in France. [10] Infection causes pain, red, dry eyes as well as abscesses on the cornea. Prognosis for ocular infections is poor, however it may be that the fungus was only able to cause infection because of reduced immune response in the patient. Treatment with antibiotics and fortified eye drops can be successful. The only other recorded ocular infection by a Scytalidium is N. dimidiatum.
Histoplasmosis is a fungal infection caused by Histoplasma capsulatum. Symptoms of this infection vary greatly, but the disease affects primarily the lungs. Occasionally, other organs are affected; called disseminated histoplasmosis, it can be fatal if left untreated.
Onychomycosis, also known as tinea unguium, is a fungal infection of the nail. Symptoms may include white or yellow nail discoloration, thickening of the nail, and separation of the nail from the nail bed. Fingernails may be affected, but it is more common for toenails. Complications may include cellulitis of the lower leg. A number of different types of fungus can cause onychomycosis, including dermatophytes and Fusarium. Risk factors include athlete's foot, other nail diseases, exposure to someone with the condition, peripheral vascular disease, and poor immune function. The diagnosis is generally suspected based on the appearance and confirmed by laboratory testing.
Talaromycosis is a fungal infection that presents with painless skin lesions of the face and neck, as well as an associated fever, anaemia, and enlargement of the lymph glands and liver.
Basidiobolus ranarum is a filamentous fungus with worldwide distribution. The fungus was first isolated by Eidam in 1886. It can saprophytically live in the intestines of mainly cold-blooded vertebrates and on decaying fruits and soil. The fungus prefers glucose as a carbon source and grows rapidly at room temperature. Basidiobolus ranarum is also known as a cause of subcutaneous zygomycosis, usually causing granulomatous infections on a host's limbs. Infections are generally geographically limited to tropical and subtropical regions such as East and West Africa. Subcutaneous zygomycosis caused by B. ranarum is a rare disease and predominantly affects children and males. Common subcutaneous zygomycosis shows characteristic features and is relatively easy to be diagnosed; while, certain rare cases might show non-specific clinical features that might pose a difficulty on its identification. Although disease caused by this fungus is known to resolve spontaneously on its own, there are a number of treatments available.
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.
Isoconazole is an azole antifungal drug and could inhibit gram positive bacteria. For foot and vaginal infections, isoconazole has a similar effectiveness to clotrimazole. Isoconazole nitrate may be used in combination with corticosteroid diflucortolone to increase its bioavailability.
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.
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.
Scytalidium is a genus of fungi in the Helotiales order. The relationship of this taxon to other taxa within the order is unknown, and it has not yet been placed with certainty into any family. This genus of anamorphic fungi has a widespread distribution and contains 18 species. Scytalidium dimidiatum causes onychomycosis in tea leaf pluckers.
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.
Microsporum nanum is a pathogenic fungus in the family Arthrodermataceae. It is a type of dermatophyte that causes infection in dead keratinized tissues such as skin, hair, and nails. Microsporum nanum is found worldwide and is both zoophilic and geophilic. Animals such as pigs and sheep are the natural hosts for the fungus; however, infection of humans is also possible. Majority of the human cases reported are associated with pig farming. The fungus can invade the skin of the host; if it is scratched off by the infected animal, the fungus is still capable of reproducing in soil.
Microascus brevicaulis is a microfungus in the Ascomycota. It is the teleomorph form of Scopulariopsis brevicaulis.Microascus brevicaulis occurs world-wide as a saprotroph in soil, a common agent of biodeterioration, an irregular plant pathogen, and an occasional agent of human nail infection.
Aspergillus ustus is a microfungus and member of the division Ascomycota. It is commonly found in indoor environments and soil. Isolated cases of human infection resulting from A. ustus have been described; however the majority of these are nail infections.
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.
Histoplasma duboisii is a saprotrophic fungus responsible for the invasive infection known as African histoplasmosis. This species is a close relative of Histoplasma capsulatum, the agent of classical histoplasmosis, and the two occur in similar habitats. Histoplasma duboisii is restricted to continental Africa and Madagascar, although scattered reports have arisen from other places usually in individuals with an African travel history. Like, H. capsulatum, H. duboisii is dimorphic – growing as a filamentous fungus at ambient temperature and a yeast at body temperature. It differs morphologically from H. capsulatum by the typical production of a large-celled yeast form. Both agents cause similar forms of disease, although H. duboisii predominantly causes cutaneous and subcutaneous disease in humans and non-human primates. The agent responds to many antifungal drug therapies used to treat serious fungal diseases.
Neoscytalidium dimidiatum was first described in 1933 as Hendersonula toruloidea from diseased orchard trees in Egypt. Decades later, it was determined to be a causative agent of human dermatomycosis-like infections and foot infections predominantly in tropical areas; however the fungus is considered to be widespread. A newer name, Scytalidium dimidiatum, was applied to a synanamorph of Nattrassia mangiferae, otherwise known as Neofusicoccum mangiferae. Substantial confusion has arisen in the literature on this fungus resulting from the use of multiple different names including Torula dimidiata, Fusicoccum dimidiatum, Scytalidium dimidiatum, and Hendersonula toruloidea. Additionally, Scytalidium lignicola and Scytalidium lignicolum are often considered earlier names of N. dimidiatum.
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.
Cephalotheca foveolata is a species of fungus. It is rarely opportunistic and generally manifests as a minor subcutaneous infection.
Mycotypha microspora, also known as Microtypha microspora, is a filamentous fungus in the division Zygomycota. It was discovered in a Citrus aurantium peel in 1932 by E. Aline Fenner, who proposed a new genus Mycotypha to accommodate it. Mycotypha africana, which is another species in the genus Mycotypha, is closely related to M. microspora. The fungus has subsequently been isolated from both outdoor and indoor settings around the world, and is typically found in soil and dung. The species rarely causes infections in humans, but has recently been involved in the clinical manifestation of the life-threatening disease mucormycosis.
Scytalidium ganodermophthorum is an anthroconidial ascomycete fungus in the Scytalidium genus. It is also known by its teleomorph name Xylogone ganodermophthora. It is the cause of yellow rot in lingzhi mushrooms and it is used in spalting as a pigmenting fungi.