Epidermophyton floccosum

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Epidermophyton floccosum
Epidermophyton floccosum 01.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Eurotiomycetes
Order: Onygenales
Family: Arthrodermataceae
Genus: Epidermophyton
Species:
E. floccosum
Binomial name
Epidermophyton floccosum
(Harz) Langeron & Miloch. (1930)
Synonyms
  • Acrothecium floccosumHarz
  • Blastotrichum floccosum(Harz) Berl. & Voglino
  • Dactylium floccosum(Harz) Sartory
  • Epidermophyton pernetti( Castell.) Nann.
  • Epidermophyton clypeiforme (MacCarthy) C.W.Dodge

Epidermophyton floccosum is a filamentous fungus that causes skin and nail infections in humans. [1] This anthropophilic dermatophyte can lead to diseases such as tinea pedis (athlete's foot), tinea cruris, tinea corporis and onychomycosis. [2] [3] Diagnostic approaches of the fungal infection include physical examination, culture testing, and molecular detection. [4] Topical antifungal treatment, such as the use of terbinafine, itraconazole, voriconazole, and ketoconazole, is often effective. [5]

Contents

E. floccosum is one of the 2 species in the genus Epidermophyton . [6] [7] During the 20th century, this species was the fourth most common cause of dermatophytosis in North America. [8] This ascomycete has a worldwide distribution but is more commonly isolated from patients in tropical and subtropical areas. [9] [2] The non-soil associated fungus has no specific growth conditions and shows characteristic smooth club-shaped macroconidia under the microscope. [2] [9]

History and taxonomy

The fungus was first isolated in 1870 from a tinea cruris patient in Germany by Carl Otto Harz, who named it Acrothecium floccosum. [10] Being unaware of Harz's work, Castellani and Sabouraud identified the species again in 1905 and 1907, respectively, and both placed the fungus into the genus Epidermophyton. [11] Epidermophyton is one of the three dermatophyte fungal genera; it is distinct from the other two genera ( Microsporum and Trichophyton ) for the absence of microconidia. [4] In 1930, based on the principle of priority, Langeron and Milochevitch renamed the fungus Epidermophyton floccosum to recognize Harz's contribution in identifying the species first, as well as his extensive morphological descriptions. [11]

Another fungus, originally named Epidermophyton stockdaleae, is a dark-brown, soil-inhabiting species that is morphologically and molecularly distinct to E. floccosum for its longer conidia and 7% NaCl tolerance. E. stockdaleae is also clinically differentiated from E. floccosum by its ability in perforating hair. [4] Due to the presence of microconidia, E. stockdaleae is now considered a synonym of Trichophyton ajelloi, hence E. floccosum is currently the only species in the genus Epidermophyton. [6] [4]

Growth and morphology

The filamentous non-soil associated fungus does not require any specific growth condition in culture. [1] [2] E. floccosum does not grow on urease culture, has low osmotolerance, and is unable to form perforating organs. [7] [12] The colonies have khaki suede-like flat surfaces and grow moderately rapidly, reaching maturity within 10 days. [6] [9] The reverse is reddish-brown. [2] Colonies are initially flat, but the centre of which later becomes raised and folded, with the periphery submerged. [4] On rich media like Sabouraud agar, colonies usually degenerate into white pleomorphic tufts within several weeks, and sometimes exude a red-brown pigment into its agar. [7]

E. floccosum has septate, hyaline hyphae. Its key features are the smooth, thin-walled, club-shaped macroconidia and the absence of microconidia. [4] The macroconidia are borne singly or in clusters of 2 or 3; they are 20–40 μm in length and 7–12 μm in width, consisting of 1 to 9 septa. [6] The narrow base and broad, club-shaped apex of the macroconidium have been compared in shape to a beaver tail. [2]

The fungus reproduces asexually through chlamydoconidia, which are resting spores that are abundant in culture. [6] [9] Arthroconidia are also abundant in the culture, emerging as swollen cells alongside macroconidia formation; these thick-walled spores are resistant to heat and drying conditions. [2]

Pathology

Infection

E. floccosum causes superficial diseases such as tinea pedis (athlete's foot) and tinea cruris, and less commonly tinea corporis and onychomycosis. [8] [4] Similar to other fungal dermatophytes, E. floccosum can invade keratinized tissues including skin and nails. [4] A recent clinical case has also demonstrated its capacity of infecting eyes, causing keratitis. [4] It does not perforate hair or hair follicles. [6] This anthropophilic dermatophyte preferentially infects humans and rarely infects animals, thus lab animal experiments are found to be unsuccessful. [6] [2] E. floccosum is more infective than most dermatophytes. [2] Chronic infections are rare, therefore maintenance of the species relies on rapid transmission between hosts. [2] The infection typically stays within the nonliving conidified layer of host epidermis, since the fungus cannot pierce through living tissues of individuals with normal immunity. However, it has been found to cause invasive infections in immunocompromised patients, demonstrating severe onychomycosis, skin lesions, and subcutaneous nodules. [4] [13]

Spread

E. floccosum can remain viable for long periods of time by producing arthroconidia in skin scales. Arthroconidia are thick-walled spores with higher resistance to drying and heat conditions than mycelium. [2] Arthroconidia formation allows E. floccosum to survive for years in showers, baths, swimming pools, towels, blankets, sheets, shoes and other clothing. [2] [8] [14] The fungus commonly spreads by contact in showers and gym facilities. [4]

Treatment

In vitro studies have found that several agents are effective against E. floccosum. [5] Disease-specific topical treatments for E. floccosum-related infections are usually effective, commonly with the use of terbinafine, itraconazole, and ketoconazole. [15]

Diagnosis

When causing the same disease, clinical demonstrations of E. floccosum are generally indistinguishable from other dermatophytes, except for tinea pedis: infections involving E. floccosum can demonstrate marked scaling in patient's toe and sole and produce punctate lesions nearby. Brownish macules could derive from some of these lesions. [4] [2]

Traditionally, diseases are diagnosed with physical and Wood's lamp examinations. Unlike some Microsporium species, Epidermophyton, as well asTrichophyton do not fluoresce under the ultraviolet light of a Wood's lamp. Fungal cultures further distinguish Epidermophyton from other dermatophytes based on the absence of microconidia. [4] Molecular advances have decreased the time of identification from 3–4 weeks to 3–4 days. Samples obtained from patient nail, hair, and skin scale can undergo PCR-RFLP, which distinguishes between 12 dermatophyte species based on their individual restriction enzyme profiles, including one for E. floccosum. A real time PCR protocol is also available for the specific detection of E. floccosum, allowing identification as fast as 4 hours after sample lysis. [4]

Habitat

E. floccosum has a worldwide distribution but is more commonly found in tropical and subtropical areas. [2] Historical fungal infections have been reported in US military in Vietnam and British Army in Southeast Asia. [8] [16] E. floccosum was considered the fourth most common cause of dermatophytosis in North America. [8] Accounting for around 20 percent US cases and 44 percent Asian cases, it is also the third most common cause of tinea pedis worldwide, following Trichophyton mentagrophytes and Trichophyton rubrum. [2]

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<span class="mw-page-title-main">Athlete's foot</span> Skin infection caused by fungus

Athlete's foot, known medically as tinea pedis, is a common skin infection of the feet caused by a fungus. Signs and symptoms often include itching, scaling, cracking and redness. In rare cases the skin may blister. Athlete's foot fungus may infect any part of the foot, but most often grows between the toes. The next most common area is the bottom of the foot. The same fungus may also affect the nails or the hands. It is a member of the group of diseases known as tinea.

Dermatophyte is a common label for a group of fungus of Arthrodermataceae that commonly causes skin disease in animals and humans. Traditionally, these anamorphic mold genera are: Microsporum, Epidermophyton and Trichophyton. There are about 40 species in these three genera. Species capable of reproducing sexually belong in the teleomorphic genus Arthroderma, of the Ascomycota. As of 2019 a total of nine genera are identified and new phylogenetic taxonomy has been proposed.

<span class="mw-page-title-main">Tinea capitis</span> Cutaneous fungal infection of the scalp

Tinea capitis is a cutaneous fungal infection (dermatophytosis) of the scalp. The disease is primarily caused by dermatophytes in the genera Trichophyton and Microsporum that invade the hair shaft. The clinical presentation is typically single or multiple patches of hair loss, sometimes with a 'black dot' pattern, that may be accompanied by inflammation, scaling, pustules, and itching. Uncommon in adults, tinea capitis is predominantly seen in pre-pubertal children, more often boys than girls.

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<span class="mw-page-title-main">Onychomycosis</span> Medical condition

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

Trichophyton rubrum is a dermatophytic fungus in the phylum Ascomycota. It is an exclusively clonal, anthropophilic saprotroph that colonizes the upper layers of dead skin, and is the most common cause of athlete's foot, fungal infection of nail, jock itch, and ringworm worldwide. Trichophyton rubrum was first described by Malmsten in 1845 and is currently considered to be a complex of species that comprises multiple, geographically patterned morphotypes, several of which have been formally described as distinct taxa, including T. raubitschekii, T. gourvilii, T. megninii and T. soudanense.

<i>Trichophyton</i> Genus of Fungi

Trichophyton is a genus of fungi, which includes the parasitic varieties that cause tinea, including athlete's foot, ringworm, jock itch, and similar infections of the nail, beard, skin and scalp. Trichophyton fungi are molds characterized by the development of both smooth-walled macro- and microconidia. Macroconidia are mostly borne laterally directly on the hyphae or on short pedicels, and are thin- or thick-walled, clavate to fusiform, and range from 4 to 8 by 8 to 50 μm in size. Macroconidia are few or absent in many species. Microconidia are spherical, pyriform to clavate or of irregular shape, and range from 2 to 3 by 2 to 4 μm in size.

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

Trichophyton tonsurans is a fungus in the family Arthrodermataceae that causes ringworm infection of the scalp. It was first recognized by David Gruby in 1844. Isolates are characterized as the "–" or negative mating type of the Arthroderma vanbreuseghemii complex. This species is thought to be conspecific with T. equinum, although the latter represents the "+" mating strain of the same biological species Despite their biological conspecificity, clones of the two mating types appear to have undergone evolutionary divergence with isolates of the T. tonsurans-type consistently associated with Tinea capitis whereas the T. equinum-type, as its name implies, is associated with horses as a regular host. Phylogenetic relationships were established in isolates from Northern Brazil, through fingerprinting polymorphic RAPD and M13 markers. There seems to be lower genomic variability in the T. tonsurans species due to allopatric divergence. Any phenotypic density is likely due to environmental factors, not genetic characteristics of the fungus.

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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.

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

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Microsporum fulvum is a wildly-distributed dermatophyte species in the Fungi Kingdom. It is known to be a close relative to other dermatophytes such as Trichophyton andEpidermophyton. The fungus is common within soil environments and grows well on keratinized material, such as hair, nails and dead skin. It is recognized as an opportunistic fungal pathogen capable of causing cutaneous mycoses in humans and animals. Originally, the fungus was thought to be Microsporum gypseum until enhanced genetic examination separated the two as distinct species in 1963.

Topical antifungaldrugs are used to treat fungal infections on the skin, scalp, nails, vagina or inside the mouth. These medications come as creams, gels, lotions, ointments, powders, shampoos, tinctures and sprays. Most antifungal drugs induce fungal cell death by destroying the cell wall of the fungus. These drugs inhibit the production of ergosterol, which is a fundamental component of the fungal cell membrane and wall.

References

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  3. ↑ Fungal infections. Diamond, Richard D., 1942-. Philadelphia: Current Medicine. 2000. ISBN   978-1573401364. OCLC   42862084.{{cite book}}: CS1 maint: others (link)
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Molecular detection of human fungal pathogens. Liu, Dongyou. Boca Raton, FL: CRC Press. 2011. pp. 421–422. ISBN   9781439812419. OCLC   783848203.{{cite book}}: CS1 maint: others (link)
  5. 1 2 Standards., National Committee for Clinical Laboratory (1998). Reference method for broth dilution antifungal susceptibility testing of conidium-forming filamentous fungi : proposed standard. Pfaller, Michael A. Wayne, Pa.: NCCLS. ISBN   9781562383558. OCLC   244296519.
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  7. 1 2 3 Biology of dermatophytes and other keratinophilic fungi. Kushwaha, Rajendra K. S., Guarro Artigas, Josep. Bilbao: Revista Iberoamericana de Micología. 2000. pp. 17–21, 30–43. ISBN   978-8460707110. OCLC   807784068.{{cite book}}: CS1 maint: others (link)
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  10. ↑ Harz OC. (1871). "Einige neue Hyphomyceten Berlins und Wiens nebst Beiträgen zur Systematik derselben" (in German). 44. Bulletin de la Société Impériale des Naturalistes de Moscou: 88–147.{{cite journal}}: Cite journal requires |journal= (help)
  11. 1 2 Langeron, M.; Milochevitch, S. (1930). "Morphologie des dermatophytes sur milieux naturels et milieux à base de polysaccharides. Essai de classification (Deuxième mémoire)" (PDF). Annales de Parasitologie Humaine et Comparée (in French). 8 (5): 465–508. doi: 10.1051/parasite/1930085465 . ISSN   0003-4150.
  12. ↑ Shadomy, H. Jean; Philpot, Christine M. (1980-08-01). "Utilization of Standard Laboratory Methods in the Laboratory Diagnosis of Problem Dermatophytes". American Journal of Clinical Pathology. 74 (2): 197–201. doi:10.1093/ajcp/74.2.197. ISSN   0002-9173. PMID   7405898.
  13. ↑ Seddon, M. E.; Thomas, M. G. (July 1997). "Invasive disease due to Epidermophyton floccosum in an immunocompromised patient with Behçet's syndrome". Clinical Infectious Diseases. 25 (1): 153–154. doi: 10.1086/516887 . ISSN   1058-4838. PMID   9243051.
  14. ↑ Cabrita, Júlia; Esteves, J.; Sequeira, Hortênsia (1973). "Dermatophytes in Portugal (1972–1981)". Mycopathologia. 84 (2–3): 159–164. doi:10.1007/BF00436527. ISSN   0301-486X. PMID   6717555. S2CID   7561260.
  15. ↑ Degreef, H. J.; DeDoncker, P. R. (September 1994). "Current therapy of dermatophytosis". Journal of the American Academy of Dermatology. 31 (3 Pt 2): S25–30. doi:10.1016/S0190-9622(08)81263-7. ISSN   0190-9622. PMID   8077504.
  16. ↑ XPharm : the comprehensive pharmacology reference. Enna, S. J., Bylund, David B., Elsevier Science (Firm). Amsterdam: Elsevier. 2008. ISBN   9780080552323. OCLC   712018683.{{cite book}}: CS1 maint: others (link)
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