Microsporum gallinae

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Microsporum gallinae
Microsporum gallinae.png
Microsporum gallinae colony growing in petri dish
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Eurotiomycetes
Order: Onygenales
Family: Arthrodermataceae
Genus: Microsporum
Species:
M. gallinae
Binomial name
Microsporum gallinae
(Mégnin ex Guéguen) Grigorakis (1929)
Synonyms

Epidermophyton gallinaeMégnin (1881)
Trichophyton gallinae(Mégnin ex Guéguen) Georg (1952)

Contents

Microsporum gallinae is a fungus of the genus Microsporum that causes dermatophytosis, commonly known as ringworm. [1] Chickens represent the host population of Microsporum gallinae but its opportunistic nature allows it to enter other populations of fowl, mice, squirrels, cats, [2] dogs and monkeys. [3] Human cases of M. gallinae are rare, and usually mild, non-life-threatening superficial infections. [2]

Taxonomy and naming

Microsporum gallinae was first identified in 1881 by Megnin from chicken favus, [4] and named Epidermophyton gallinae. [5] It was later transferred from the Epidermophyton genus, and classified in the Trichophyton genus, as T. gallinae. [4]

The identification of rough-walled macroconidia, a hallmark of the Microsporum genus, lead to the dermatophyte being classified as M. gallinae. [1] [4] There is still debate about the phylogenetic placement of this dermatophyte, but the accepted name is Microsporum gallinae. [5] Analysis of its DNA sequences by PCR shows M. gallinae is most closely related to Microsporum vanbreuseghemii and Arthroderma grubyi , both are also zoophilic fungi. [3] [6]

Distribution

Microsporum gallinae is distributed throughout the world, with cases reported in: Europe, the Middle East, South America, North America, Africa and Japan. [2] The fungus seems to be isolated more often in areas with high humidity and temperature. [3]

Morphology

In culture, M. gallinae produces a white, satiny colony. [7] [8] The colony appears flat with radial folds and irregular edges as it grows in culture [7] The colony reverse produces a strong pigmentation that changes from pink to a deep red and diffuses through the growth medium. [5] [7] [8] Optimal growth of M. gallinae occurs at 26-28 °C, [3] and no special nutritional requirements are necessary for its growth. [9] Additionally, M. gallinae is urease positive. [9]

During sporulation, septate hyphae, [2] [7] with macroconidia with tappered tips, and club shaped microconidia are present. [7] [8] [10] The addition of thiamine or yeast extracts promotes sporulation of M. gallinae. [7] Hair invasion observed in M. gallinae is large spored ectothrix type, meaning that the spores form outside of the hair shaft. [5]

Pathogenicity

Microsporum gallinae is a cosmopolitan zoophilic fungi that very rarely affects humans. [10] It obtains nutrients from keratin-rich skin, nails and hair, releasing enzymes during its digestion that elicit a host immune response as seen in ringworm. [11] [12] Microsporum gallinae infection is diagnosed by culturing the scrapings from skin lesions. [9]

Chickens

Microsporum gallinae causes a superficial infection [13] that forms white lesions on the wattles and combs of chickens. [1] [10] Lesions may spread to the head and neck. [2] The feathers are normally not affected by the dermatophyte, although some feather loss can occur. [1] Roosters and chicks tend to be more susceptible to the infection, with fighting cocks having the highest rates of M. gallinae dermatophytosis. [2] Although, it tends to resolve with treatment, the M. gallinae infection may become chronic. [1] The lesions can also become infected with bacteria, complicating the infection. [1] In some cases, it can resolve naturally without treatment; however, the infection may persist for weeks prior to clearance. [5]

Humans

Microsporum gallinae has been isolated from the scalp, and smooth skin in human populations. [10] Microsporum gallinae infections are most commonly tinea capitis and tinea corporis. [3] Very few human cases of M. gallinae infection have been reported, none of which were life-threatening. [9] Of the reported cases, individuals ranged from 3–96 years old. [3] They had cutaneous lesions on the glabrous skin or the scalp. [3] These localized lesions are frequently accompanied by itching. [2] [9] The cutaneous manifestations are very similar to those of Microsporum canis therefore many cases of Microsporum gallinae could have been unreported. [3]

In rare cases, immunocompromised individuals form severe dissemination on the skin, instead of small localized lesions [3] as a result of handling infected animals. [2] [9] Only one case of extensive dermatophytosis was reported involving M. gallinae infection of a person with AIDS. [2] [3] [9]

Treatment

The treatment of M. gallinae involves both topical and oral antifungals. [1] [3] Topical antifungals, such as: Terbinafine, [3] Tolnaftate, [1] and orally administered Griseofulvin [1] [9] have been used successfully to treat M. gallinae infections in humans and animals.

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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 corporis</span> Medical condition

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<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.

<span class="mw-page-title-main">Dermatophytosis</span> Fungal infection of the skin

Dermatophytosis, also known as ringworm, is a fungal infection of the skin. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Symptoms begin four to fourteen days after exposure. Multiple areas can be affected at a given time.

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

Kerion or kerion celsi is an acute inflammatory process which is the result of the host's response to a fungal ringworm infection of the hair follicles of the scalp that can be accompanied by secondary bacterial infection(s). It usually appears as raised, spongy lesions, and typically occurs in children. This honeycomb is a painful inflammatory reaction with deep suppurative lesions on the scalp. Follicles may be seen discharging pus. There may be sinus formation and rarely mycetoma-like grains are produced. It is usually caused by dermatophytes such as Trichophyton verrucosum, T. mentagrophytes, and Microsporum canis. Treatment with oral griseofulvin common.

<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>Microsporum audouinii</i> Species of fungus

Microsporum audouinii is an anthropophilic fungus in the genus Microsporum. It is a type of dermatophyte that colonizes keratinized tissues causing infection. The fungus is characterized by its spindle-shaped macroconidia, clavate microconidia as well as its pitted or spiny external walls.

<span class="mw-page-title-main">Fungal folliculitis</span> Inflammation of hair follicles due to fungal infection

Majocchi's granuloma is a skin condition characterized by deep, pustular plaques, and is a form of tinea corporis. It is a localized form of fungal folliculitis. Lesions often have a pink and scaly central component with pustules or folliculocentric papules at the periphery. The name comes from Domenico Majocchi, who discovered the disorder in 1883. Majocchi was a professor of dermatology at the University of Parma and later the University of Bologna. The most common dermatophyte is called Trichophyton rubrum.

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

Microsporum gypseum is a soil-associated dermatophyte that occasionally is known to colonise and infect the upper dead layers of the skin of mammals. The name refers to an asexual "form-taxon" that has been associated with four related biological species of fungi: the pathogenic taxa Arthroderma incurvatum, A. gypsea, A. fulva and the non-pathogenic saprotroph A. corniculata. More recent studies have restricted M. gypseum to two teleomorphic species A. gypseum and A. incurvatum. The conidial states of A. fulva and A. corniculata have been assigned to M. fulvum and M. boullardii. Because the anamorphic states of these fungi are so similar, they can be identified reliably only by mating. Two mating strains have been discovered, "+" and "–". The classification of this species has been based on the characteristically rough-walled, blunt, club-shaped, multicelled macroconidia. Synonyms include Achorion gypseum, Microsporum flavescens, M. scorteum, and M. xanthodes. There has been past nomenclatural confusion in the usage of the generic names Microsporum and Microsporon.

<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.

Trichophyton concentricum is an anthropophilic dermatophyte believed to be an etiological agent of a type of skin mycosis in humans, evidenced by scaly cutaneous patches on the body known as tinea imbricata. This fungus has been found mainly in the Pacific Islands and South America.

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>Aphanoascus fulvescens</i> Species of fungus

Aphanoascus fulvescens is a mould fungus that behaves as a keratinophilic saprotroph and belongs to the Ascomycota. It is readily isolated from soil and dung containing keratin-rich tissues that have been separated from their animal hosts. This organism, distributed worldwide, is most commonly found in areas of temperate climate, in keeping with its optimal growth temperature of 28 °C (82 °F). While A. fulvescens is recognized as a geophilic fungal species, it is also a facultative opportunistic pathogen. Although it is not a dermatophyte, A. fulvescens has occasionally been shown to cause onychomycosis infections in humans. Its recognition in the laboratory is clinically important for correct diagnosis and treatment of human dermal infections.

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

Favus or tinea favosa is the severe form of tinea capitis, a skin infectious disease caused by the dermatophyte fungus Trichophyton schoenleinii. Typically the species affects the scalp, but occasionally occurs as onychomycosis, tinea barbae, or tinea corporis.

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

Trichophyton verrucosum, commonly known as the cattle ringworm fungus, is a dermatophyte largely responsible for fungal skin disease in cattle, but is also a common cause of ringworm in donkeys, dogs, goat, sheep, and horses. It has a worldwide distribution, however human infection is more common in rural areas where contact with animals is more frequent, and can cause severe inflammation of the afflicted region. Trichophyton verrucosum was first described by Emile Bodin in 1902.

<i>Epidermophyton floccosum</i> Species of fungus

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

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.

References

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