Microsporum Fulvum
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''Microsporum fulvum'' is a wildly-distributed
dermatophyte Dermatophyte (from Greek '' derma'' "skin" ( GEN ''dermatos'') and ''phyton'' "plant") is a common label for a group of fungus of '' Arthrodermataceae'' that commonly causes skin disease in animals and humans. Traditionally, these anamorphic ( ...
species in the
Fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
Kingdom. It is known to be a close relative to other dermatophytes such as ''
Trichophyton ''Trichophyton'' is a genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV c ...
and'' ''
Epidermophyton ''Epidermophyton'' is a genus of fungus causing superficial and cutaneous mycoses, including ''E. floccosum'', and causes tinea corporis (ringworm), tinea cruris (jock itch), tinea pedis (athlete's foot), and tinea unguium Dermatophytosis ...
.'' 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 Fungal infection, also known as mycosis, is a disease caused by fungi. Different types are traditionally divided according to the part of the body affected: superficial, subcutaneous, and systemic. Superficial fungal infections include common ...
in humans and animals. Originally, the fungus was thought to be ''
Microsporum gypseum ''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 biol ...
'' until enhanced genetic examination separated the two as distinct species in 1963.


History and taxonomy

''Microsporum fulvum'' was first documented in 1909 as ''Microsporum gypseum'' by Weitzman et al. ( Argentina Medical Society)''.'' The fungus was thought to be the imperfect state of the
anamorphic Anamorphic format is a cinematography technique that captures widescreen images using recording media with narrower native Aspect ratio (image), aspect ratios. Originally developed for 35 mm movie film, 35 mm film to create widescreen pres ...
, asexually reproducing, ''M. gypseum.'' However, in Stockdale (1963) ''M. fulvum'' was considered and described as its own species, '' Nannizzia fulva'', the perfect state of the fungus. In the present, ''M. fulvum'' is still referred to as part of the ''Microsporum gypseum complex.'' This complex includes the three distinct species: ''Microsporum gypseum'', ''Microsporum fulvum'' and ''Microsporum incurvatum.'' Each of these fungi possess a high degree of morphological similarity but do have significant genetic differences accounting for the speciation.


Growth

''Microsporum fulvum'' will grow well on soil in a wide-variety of climate conditions and is found in world-wide distribution. The fungus tends to colonize keratin-rich environments and will grow rapidly in
culture Culture ( ) is a concept that encompasses the social behavior, institutions, and Social norm, norms found in human societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, Attitude (psychology), attitudes ...
or in nature at diverse temperatures. ''M. fulvum'' commonly occupies materials such as dead skin cells and fragmented hair filaments. In culture, growth will occur within 4–5 days and forms floccose, wooly colonies. The clustered cells appear granular with a sandy-brown tinge where most compact and a less dense, whiter periphery.


Morphology

''M. fulvum'' looks morphologically similar to ''Microsporum gypseum.'' The fungus propagates sexually reproductive asci that are 5-7 microns large with up to 8 spores, which are densely packed with
ascospore In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...
s. Asexual
macroconidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word f ...
are also formed and appear in large clusters (up to 8 microns in diameter) with
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 o ...
e branches. The macroconidia are fusoid-shaped with tapered ends and have very thin walls.
Microconidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ca ...
are drop-shaped and are observed with sparse, irregular hyphae. When grown on soil combined with horse hair, closed fruiting bodies called
cleistothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascoc ...
form.


Reproduction

''Microsporum fulvum'' is classified as a
teleomorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...
ic species as it sexually reproduces. This sexual state has been referred to as ''Arthroderma fulvum.'' Two
mating type Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct sexes. They also occur in multicellular organisms such as fungi. Definition Mating types are the microorganism equival ...
s have been distinguished for the sexual reproduction of the fungus and are characterized with (+) and (-). The (+) mating type synthesizes the
elastase In molecular biology, elastase is an enzyme from the class of proteases (peptidases) that break down proteins, specifically one that can break down elastin. In other words, the name only refers to the substrate specificity (i.e. what proteins i ...
enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
, where as the (-) mating type is unable to produce the elastase. Experiments involving the mating types suggest that the (+) mating type has higher virulence and causes more cases of infection. However, both strains demonstrate a positive result for their ability to hydrolyze the
urea Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...
molecule, indicating the presence of the
urease Ureases (), functionally, belong to the superfamily of amidohydrolases and phosphotriesterases. Ureases are found in numerous Bacteria, Archaea, fungi, algae, plants, and some invertebrates. Ureases are nickel-containing metalloenzymes of high ...
enzyme. A conducted study showed that a majority of tested isolates (>50%) of ''M. fulvum'' tested positive for urea hydrolysis within 0–7 days, and almost all isolates tested positive within 10–12 days, suggesting rapid growth of the organism.


Habitat and ecology

Like many other dermatophytes, ''M. fulvum'' is a soil-loving, geophilic organism. The species is commonly found invading obsolete hair fibres and skin molecules which are made of keratin proteins. It can be found growing on the keratinized material of many different mammalian species including humans, horses, rodents, dogs, etc. without perceived preference. However, a higher incidence of colonization of ''M. fulvum'' has been documented on the epidermis of hedgehogs without causing any serious skin lesions, suggesting a commensal relationship between the organisms. Isolates of the fungus have been found in skin and lung samples of healthy rodents without indication of impairment. As well, other ''Microsporum'' species have arthrospores that are known to remain on human scalp hairs for months without causing skin lesions. Due to the similar behavioural description of species in the ''Microsporum'' genus, it is believed that penetration of the
mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...
is necessary for the fungus to become infectious to the host, otherwise the fungal organism can coexist without harm. Geographically, ''Microporum fulvum'' has been found in diverse climate regions world-wide. The distribution of the fungus seems to be very broad and indiscriminate to temperature fluctuations. Isolates have been documented in
Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
,
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
,
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
,
Gabon Gabon ( ; ), officially the Gabonese Republic (), is a country on the Atlantic coast of Central Africa, on the equator, bordered by Equatorial Guinea to the northwest, Cameroon to the north, the Republic of the Congo to the east and south, and ...
,
Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...
and many more geographically distinct areas. The fungus is commonly isolated in Canadian soils, however few infections have been reported. After a 20-year-old man in Iran was diagnosed with a ''M. fulvum'' fungal infection, a study was conducted on Iranian soil cultures from regions of varying temperatures. Experiments concluded that ''M. fulvum'' is colonized in the soils of a wide variety of environmental regions.


Detection

A mechanism termed baiting can be used to attract ''Microsporum fulvum'' to specific soil samples. The method involves preparing the desired soil with keratinized molecules (hair fragments, nail clippings, etc.) and waiting for colonization of fungus onto the material. Once fungal collections populate the sample, morphological examination can be conducted and completed. Morphological analysis is used to distinguish ''Microsporum'' species from other keratin-loving dermatophytes. To accurately decipher ''Microsporum gypseum and'' ''Microsporum fulvum'' from one another, many researchers use genetic analysis procedures.
PCR amplification The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...
and
genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
can be used to uncover information about the
mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...
, which differs between the two species. In clinical reports, researchers have used methods referred to as
Internal Transcribed Spacer Internal transcribed spacer (ITS) is the spacer DNA situated between the small-subunit ribosomal RNA (rRNA) and large-subunit rRNA genes in the chromosome or the corresponding transcribed region in the polycistronic rRNA precursor transcript. ...
(ITS) Sequencing and Matrix-assisted laser desorption/ionization (Maldi-TOF)
Mass Spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...
to differentiate the species of the ''Microsporum gypseum complex''.


Disease


Pathogenicity

''Microsporum fulvum'' causes infection in humans, similar to the
ringworm Dermatophytosis, also known as tinea and ringworm, is a mycosis, fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the a ...
infection caused by ''Microsporum gypseum'' that can lead to disease progression. ''M. fulvum'' has been reported in cases of
dermatophytosis Dermatophytosis, also known as tinea and ringworm, is a fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area aff ...
,
cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different d ...
mycoses Fungal infection, also known as mycosis, is a disease caused by fungi. Different types are traditionally divided according to the part of the body affected: superficial, subcutaneous, and systemic. Superficial fungal infections include common ...
on any
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...
ized tissue (dead skin).
Tinea corporis Tinea corporis is a fungal infection of the body, similar to other forms of tinea. Specifically, it is a type of dermatophytosis (or ringworm) that appears on the arms and legs, especially on glabrous skin; however, it may occur on any superfici ...
refers to the generic ringworm infection that can occur on any area of the body.
Tinea pedis Dermatophytosis, also known as tinea and ringworm, is a fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area aff ...
is commonly referred to as
Athlete's Foot 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 ...
and involves ''Microsporum'' fungi infecting the feet.
Tinea capitis Tinea capitis (also known as "herpes tonsurans", "ringworm of the hair", "ringworm of the scalp", "scalp ringworm", and "tinea tonsurans") is a cutaneous fungal infection ( dermatophytosis) of the scalp. The disease is primarily caused by dermato ...
refers to ''Microsporum'' fungi infection of the scalp. Each of these can be caused by ''Microsporum fulvum'', as well as other fungi, and elicit a similar immune response leading to dry patches, rashes, redness, edema, etc. in a localized area. Research shows that most infections from ''M. fulvum'' will have a duration of approximately one month and regress on their own, with the exception of more severe cases that require treatment. These mycoses are restricted to keratinized tissue and remain localized as non-systemic infections. The causative agent of disease are fungal
keratinase Keratinases are proteolytic enzymes that digest keratin. They hold industrial promise, as they can turn keratin-rich farm waste such as feather meal into more digestible fragments. History They were initially classified as 'proteinases of unk ...
s, which degrade dead material and break down tissue. However, defense mechanisms are present within mammalian blood serum that inhibit these molecules and do not allow the fungus to travel throughout the body in the circulatory system. If the fungus gains access to mucosal membranes, it begins to release the
elastase In molecular biology, elastase is an enzyme from the class of proteases (peptidases) that break down proteins, specifically one that can break down elastin. In other words, the name only refers to the substrate specificity (i.e. what proteins i ...
enzyme as well, which is responsible for causing an
inflammatory response Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...
in the host.


Transmission

Initial infections with ''Microsporum fulvum'' are most likely from indirect sources where the fungus inhabited soil that came into contact with the mucous membrane of an animal. New infections can arise through direct or indirect contact of animals and humans who have been introduced to another contaminated source. Often transmission involves the shared use of clothing (shoes- tinea pedis, hats- capitis, etc.). Incidence of infection cases increase in winter months with cold climates due to continued use of closed-toed footwear which provide a good environment for fungal growth. Symptoms of infection are also exacerbated and more severe in these conditions. Initial infections are common in those with high contact to soil and plant material, such as gardeners. Secondary contamination of ''M. fulvum'' often occurs in bursts with multiple infections. In 1949, there were 8 cases of microsporosis caused by ''M. fulvum'' that were all in children under the age of 10 who lived in the same neighbourhood of
Indiana Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...
. Thus, the fungus can spread through contact transmission.


Treatment and prevention

Due to the biological properties and transmission methods of ''M. fulvum,'' proper
hygienic Hygiene is a set of practices performed to preserve health. According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...
practices assist with prevention of infection, especially regarding tinea pedis (infection of the feet). Health officials recommend the avoidance of contaminated flooring, such as locker rooms where fungi grow rapidly. In past reports, treatment methods for ''Microsporum gypseum'' infections have been effective for ''M. fulvum'' infections. Anti-fungal drugs may be prescribed. As few infections have been confirmed to be caused by ''M. fulvum'', little data has become available on treatment options. However, one confirmed infection in an Iranian man had been treated with oral
terbinafine Terbinafine, sold under the brand name Lamisil among others, is an antifungal medication used to treat pityriasis versicolor, onychomycosis, fungal nail infections, and ringworm including jock itch and athlete's foot. It is either oral adminis ...
(
antifungal drug An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as c ...
) and the infection cleared.


Biotechnology applications

Keratinase Keratinases are proteolytic enzymes that digest keratin. They hold industrial promise, as they can turn keratin-rich farm waste such as feather meal into more digestible fragments. History They were initially classified as 'proteinases of unk ...
is an enzyme that functions to break down and degrade keratin molecules. ''Microsporum fulvum'' has the ability to synthesize keratinase and utilize the enzyme to inhabit and exploit the environment in which it resides. Poultry industries have become interested in organisms which intrinsically produce keratinase for the reasoning that chicken feathers, which have high levels of dense keratin, are tough to break down and utilize. Fungal keratinase could be cultivated to break down chicken feathers into smaller products which could be converted into other material, such as
animal feed Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word ''feed'' more often refers to fodder. Animal feed is an important input ...
.


References

{{Taxonbar, from=Q10584820 Arthrodermataceae Fungus species