Trichophyton tonsurans

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Trichophyton tonsurans
Ttonsurans011.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Eurotiomycetes
Order: Onygenales
Family: Arthrodermataceae
Genus: Trichophyton
Species:
T. tonsurans
Binomial name
Trichophyton tonsurans
Malmsten (1848)

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. [1] 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 (particularly in children) whereas the T. equinum-type, as its name implies, is associated with horses as a regular host. [2] 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. [3] Any phenotypic density is likely due to environmental factors, not genetic characteristics of the fungus. [3]

Contents

Colony morphology

Colony of Trichophyton tonsurans from scalp scraping cultured on Sabouraud's dextrose agar with cycloheximide, chloramphenicol and gentamicin (7 d) T tonsurans colony 800.jpg
Colony of Trichophyton tonsurans from scalp scraping cultured on Sabouraud's dextrose agar with cycloheximide, chloramphenicol and gentamicin (7 d)

Trichophyton tonsurans may be identified through analysis of its fast-growing colonies. [4] Colonies tend to be flat, powdery, and yellow with a reddish undercolour. It develops into a folded colony, and may vary in colour from off-white to grey, with dark pigments that may diffuse into the medium. [5] The younger colonies fluoresce green on Sabouraud's agar, [5] and are also flat, but are mahogany red or lemon-yellow coloured. [4] On this agar the fungus grows peripherally and develops into a flatter, creamy disk with raised edges. [1] Trichophyton tonsurans also produces many inflated, pear-shaped microconidia, borne on matchstick-like stalks. It also forms fewer macroconidia that are 4-6 cells long, with thick cell walls. [4]

A different simple method for identification at early stages is through the detection of chlamydospore-like structures (CLS), which are found on the reverse side of the culture under light microscopy. Chlamydospores are asexual spores that are created through hyphal modification, often with thick cell walls arising from the deposition of hydrophobic materials along the original cell wall. [6] After inoculation on culture media (such as commonly used Mycosel agar), mycelia extend into the media and create the CLS. Normally, strains will produce CLS regardless of the media it is grown on. [6] CLS growth is essentially unaffected by antibiotic treatment with chloramphenicol, as well as by cycloheximide. [6] After 5 days of incubation, CLS production will be evident, suggesting the fungus is highly likely to be T. tonsurans. [6]

Responses of T. tonsurans to different growth conditions and nutrient media is useful in aiding identification. For example, growth is enhanced in the presence of thiamine, [5] and this exogenous requirement for thiamine distinguishes T. tonsurans from similar species. [4] Since thiamine stimulates growth, T. tonsurans also displays this behaviour on vitamin-free, thiamine-supplemented casamino acids agar but the growth is more sparse, and subsurface growth is absent. [4] BCP-milk solids glucose agar can also be used as an indicator of this fungus. This medium turns from pale blue to purple in colour in 7–14 days of growth at 25 °C (77 °F). The colour change is due to an alkaline shift arising from the release of ammonium during protein hydrolysis. [4]

Epidemiology

Trichophyton tonsurans causes tinea capitis infection globally, but it is especially endemic in Latin America (especially northern Brazil), [3] Mexico, and Africa. [4] Infections due to this species have become increasingly common in the United States and Canada since the 1980s as a consequence of changing patterns in global travel and immigration, and it is responsible for a majority of pediatric tinea capitis infections in the US. [3] [5]

The modes of dispersal are unclear, though it is associated with homes, schools and other institutions, and barbershops. [7] Transmission can occur through direct transfer, or through the use of shared resources and facilities such as pillows, couches, rugs, and pets, which should be thoroughly examined because they can be carriers of T. tonsurans. [7] Children are most susceptible to Tinea capitis whereas adult infections more often manifest as tinea corporis. [4] This species is a major cause of family and institutional outbreaks because of its persistent nature in indoor environments, and its ability to be transmitted through asymptomatic carriers. [4]

Pathophysiology

Once the fungal infection has been contracted, it invades hairs and sporulates in the hair shaft, causing it to burst and curl, creating a black dot on the scalp. [5] Tinea capitis is the clinical disease, but it may also cause Tinea corporis, onychomycosis, and Tinea pedis. [5] Cutaneous lesions due to T. tonsurans do not fluoresce under Wood's Lamp. [8] Although some people may not show the symptoms of carrying T. tonsurans, it has a distinctive manifestation. During pathogenesis, the fungus undergoes protease elaboration to hydrolyze structural proteins (such as the keratin found in hair), and isolates show peak values between days 18–22 during the sporulation phase. [9]

There are potentially 23 genes that may have mechanistic roles of this skin infection, and 21 show significant differences in infection rates, especially among children. The genes are typically involved in leukocyte activation and migration, and formation and integrity of the extracellular matrix. [10] In molecular studies of its virulence, common target genes include CarbM14, CER, and Sub2, which encode the proteases carboxypeptidase, ceraminidase, and subtilisin, respectively. Among other virulence-related enzymes, T. tonsurans also produces urease. [3]

This fungus has also been found to produce melanin, which may be phenotypically demonstrated through in vitro induction in caffeic acid media. Melanin acts as an antioxidant molecule, providing protective properties to the fungus from damaging UV rays. Since it is endemic in sunny regions, the melanin production is perhaps crucial for survival. [3]

In early stages of infection, the lesion has a clear and raised border, although there is not much hair loss yet. [1] However, as it progresses, infected hairs break off at the scalp surface and the scalp is eventually coated in a scaly layer, with short hair stubs remaining. Twisted hairs may be found in keratotic follicular papules that will be formed. [1] The infection is often called "black dot ringworm" due to the small dark hair stubs that are found on the scalp. [11] Inflammatory reactions are also quite common and can manifest as edema, abscess, [1] or highly inflammatory kerion. [11] Hair regrowth does occur, although some scarring may remain. [1] Males have a tendency to show greater improvement in non-inflammatory presentation as well. [11] Although there are several treatments available, tinea capitis often has no subjective symptoms, so people at risk for infection should still receive fungal examinations regularly. [12]

Treatment

Treatment options include antifungal shampoo, [13] systemic antifungals, or both. Oral therapy is indicated for complicated infections of those that fail to respond to topical treatment. Still, the use of selenium sulphide or povidone-iodine shampoos greatly reduce fungal viability and may be helpful in person-to-person transmission. [7] Advancements have been made in detection of T. tonsurans in patients with Tinea capitis, using TaqMan PCR assay and primers and probes designed to detect this fungus rapidly and specifically, excluding contaminating skin microorganisms. [12]

Related Research Articles

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.

<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.

<span class="mw-page-title-main">KOH test</span> Test to differentiate between skin fungi

The KOH Test for Candida albicans, also known as a potassium hydroxide preparation or KOH prep, is a quick, inexpensive fungal test to differentiate dermatophytes and Candida albicans symptoms from other skin disorders like psoriasis and eczema.

<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.

<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>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.

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>Microsporum gallinae</i> Species of fungus

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

Myriodontium keratinophilum is a fungus widespread in nature, most abundantly found in keratin-rich environments such as feathers, nails and hair. Despite its ability to colonize keratinous surfaces of human body, the species has been known to be non-pathogenic in man and is phylogentically distant to other human pathogenic species, such as anthropophilic dermatophytes. However, its occasional isolation from clinical specimens along with its keratinolytic properties suggest the possibility it may contribute to disease.

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

  1. 1 2 3 4 5 6 Price, Harold; Taylor, David R. (1952). "Trichophyton tonsurans (crateriforme) infection of the scalp". California Medicine. 76 (4). PMID   14925831.
  2. ↑ Gräser, Yvonne; Scott, James; Summerbell, Richard (14 May 2008). "The New Species Concept in Dermatophytes—a Polyphasic Approach". Mycopathologia. 166 (5–6): 239–256. CiteSeerX   10.1.1.681.6863 . doi:10.1007/s11046-008-9099-y. PMID   18478366.
  3. 1 2 3 4 5 6 Sidrim, JJ; Rocha, MF; Leite, JJ; Maranhão, FC; Lima, RA; Castelo-Branco Dde, S; Bandeira Tde, J; Cordeiro Rde, A; Brilhante, RS (November 2013). "Trichophyton tonsurans strains from Brazil: phenotypic heterogeneity, genetic homology, and detection of virulence genes". Canadian Journal of Microbiology. 59 (11): 754–60. doi:10.1139/cjm-2013-0670. PMID   24206358.
  4. 1 2 3 4 5 6 7 8 9 al.], Julius Kane ... [et (1997). Laboratory handbook of dermatophytes : a clinical guide and laboratory handbook of dermatophytes and other filamentous fungi from skin, hair, and nails. Belmont, CA: Star Pub. ISBN   978-0898631579.
  5. 1 2 3 4 5 6 Rebell, Gerbert; Taplin, David; Blank, Harvey (1964). Dermatophytes Their Recognition and Identification. Miami, FL: Dermatology Foundation of Miami.
  6. 1 2 3 4 Mochizuki, Takashi; Anzawa, Kazushi; Sakata, Yuichi; Fujihiro, Machiko (2013). "Simple identification of by chlamydospore-like structures produced in culture media". The Journal of Dermatology. 40 (12): 1027–1032. doi:10.1111/1346-8138.12354. PMID   24304336.
  7. 1 2 3 Ilkit, Macit; Demirhindi, Hakan (23 November 2007). "Asymptomatic dermatophyte scalp carriage: laboratory diagnosis, epidemiology and management". Mycopathologia. 165 (2): 61–71. doi:10.1007/s11046-007-9081-0. PMID   18034369.
  8. ↑ Asawanonda, P; Taylor, CR (November 1999). "Wood's light in dermatology". International Journal of Dermatology. 38 (11): 801–7. doi:10.1046/j.1365-4362.1999.00794.x. PMID   10583611.
  9. ↑ Gokulshankar, S; Ranjitsingh, AJA; Venkatesan, G; Ranjith, MS; Vijayalakshmi, GS; Prabhamanju, M; Subashini, S (2010). "Is moderation of protease production an adaptation of well-defined anthropization in dermatophytes?". Indian Journal of Pathology and Microbiology. 53 (1): 87–92. doi: 10.4103/0377-4929.59191 . PMID   20090230.
  10. ↑ Nenoff, P; Krüger, C; Ginter-Hanselmayer, G; Tietz, HJ (March 2014). "Mycology – an update. Part 1: Dermatomycoses: causative agents, epidemiology and pathogenesis". Journal der Deutschen Dermatologischen Gesellschaft. 12 (3): 188–209, quiz 210, 188–211, quiz 212. doi:10.1111/ddg.12245. PMID   24533779.
  11. 1 2 3 Gupta, A.K.; Summerbell, R.C. (March 2000). "Tinea Capitis". Medical Mycology. 38 (4): 255–287. doi: 10.1080/714030949 . PMID   10975696.
  12. 1 2 Sugita, T.; Shiraki, Y.; Hiruma, M. (2006). "Real-time PCR TaqMan assay for detecting, a causative agent of tinea capitis, from hairbrushes". Medical Mycology. 44 (6): 579–581. doi: 10.1080/13693780600717153 . PMID   16966179.
  13. ↑ Pomeranz, AJ; Sabnis, SS; McGrath, GJ; Esterly, NB (May 1999). "Asymptomatic dermatophyte carriers in the households of children with tinea capitis". Archives of Pediatrics & Adolescent Medicine. 153 (5): 483–6. doi: 10.1001/archpedi.153.5.483 . PMID   10323628.
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