Trichophyton is a genus of fungi that comprises the parasitic species responsible for tinea, athlete’s foot, ringworm, jock itch, and similar infections of the nail, beard, skin, and scalp. Trichophyton fungi are characterized by the development of both macro- and microconidia with smooth walls. Macroconidia are thin- or thick-walled, clavate to fusiform, and range in size from 4 to 8 by 8 to 50 μm. They are typically borne laterally directly on hyphae or on short pedicels. Macroconidia are uncommon or absent in numerous species. Microconidia are spherical, pyriform to clavate, or irregular in shape, with dimensions ranging from 2 to 3 by 2 to 4 μm.

The following are some of the most common Trichophyton species:

• Trichophyton rubrum
• Trichophyton mentagrophytes
• Trichophyton tonsurans
• Trichophyton verrucosum
• Trichophyton schoenleinii

Habitat of Trichophyton spp

Trichophyton spp. is a genus of fungi that can induce numerous skin infections in humans and animals. Typically, they are found in soil, on animals, and on humans. Depending on the species, the habitat of Trichophyton spp. can vary.

• Anthropophilic species prefer to feed on humans. This species is the leading cause of ringworm in humans. These organisms inhabit the epidermis, hair, and nails.
• Zoophilic organisms are those that prefer to feed on other animals. Through contact with an infected animal, these species can be transmitted to humans. Ringworm can affect the epidermis, hair, and nails.
• Geophilic species favor living in the soil. Typically, these species do not cause human infections, but they can occasionally be transmitted through contact with contaminated soil.

Some Trichophyton spp. species are cosmopolitan, which means they can be found all over the globe. Other species have a more restricted distribution. Trichophyton indotineae, for instance, is believed to have originated on the Indian subcontinent and is now found in tropical and subtropical regions worldwide.

In mild and humid environments, the risk of infection by Trichophyton spp. increases. This is because these conditions are optimal for fungus proliferation. Contact with an infected person or animal and inadequate personal hygiene are additional risk factors.

Morphology of Trichophyton spp

• Hyphae: The hyphae of Trichophyton spp. are septate, meaning they are separated into compartments by cross walls. This is a trait shared by all fungi. Additionally, the hyphae branch, allowing the fungus to develop and spread.
• Microconidia: Microconidia are produced by the branching of hyphae into microconidia. They are typically spherical, pyriform, or clavate and have a diameter of 1-2 micrometers. Trichophyton spp. do not always produce microconidia, and their presence can vary depending on the fungus species.
• Macroconidia: Macroconidia are generated by a specialized structure known as a conidiophore. The macroconidia are carried by a long, slender stalk called the conidiophore. Macroconidia are typically clavate or fusiform and may be unicellular or multicellular. They typically range in diameter from 4 to 8 micrometers. Macroconidia are a crucial diagnostic characteristic for identifying Trichophyton species.

Cultural Characteristics of Trichophyton spp

Several cultural characteristics of Trichophyton spp. can be used to identify and diagnose dermatophyte infections. These features consist of:

• Colony morphology: Depending on the species, colonies of Trichophyton spp. can vary in size, shape, and pigment. They are typically granular or velvety in texture and white, cream, or gray in color.
• Growth rate: The growth rate of Trichophyton spp. colonies on Sabouraud dextrose agar (SDA) is brisk. In 7-10 days, they can attain a diameter of 1-2 cm.
• Temperature tolerance: Trichophyton spp. are typically mesophilic, meaning they grow optimally at temperatures between 25 and 30 degrees Celsius. Nevertheless, certain species can thrive at temperatures as high as 40 degrees Celsius.
• pH tolerance: Trichophyton spp. are typically neutralophilic, meaning they thrive at a pH range between 6.5-7. However, some species can thrive at pH levels between 5 and 8.
• Nutritional requirements: Trichophyton spp. are heterotrophic, so they require organic nutrients for growth. They are also auxotrophic, meaning that they cannot synthesize certain vitamins and amino acids on their own.

Some Species of Trichophyton

Trichophyton is a genus of fungi that includes several species responsible for causing skin infections in humans and animals. Some of the selected species of Trichophyton include:

• Trichophyton rubrum: This is one of the most common species of Trichophyton and is responsible for causing various dermatophytosis such as athlete’s foot, jock itch, and ringworm. It typically grows at 30-35°C and produces red pigment on certain media.
• Trichophyton mentagrophytes: This species is a common cause of dermatophytosis in both humans and animals. It typically grows at 25-30°C and produces macroconidia with smooth, rounded ends.
• Trichophyton tonsurans: This species is commonly associated with scalp infections such as tinea capitis in children. It typically grows at 25-30°C and produces numerous microconidia and macroconidia.
• Trichophyton interdigitale: This species is responsible for causing infections between the toes (interdigital spaces) and other areas of the foot. It typically grows at 25-30°C and produces both macroconidia and microconidia.
• Trichophyton verrucosum: This species is responsible for causing dermatophytosis in cattle and other animals. It typically grows at 25-30°C and produces both macroconidia and microconidia.
• Trichophyton schoenleinii: This species is known to cause a type of ringworm called favus, which affects the scalp and causes characteristic yellow crusts. It can also affect other parts of the body, including the nails.
• Trichophyton violaceum: This species is a rare cause of dermatophytosis, but it has been reported to cause infections in various parts of the body, including the scalp, nails, and skin.
• Trichophyton equinum: This species is primarily found in horses and can cause infections in humans who come into contact with infected animals. It is known to cause infections in the scalp, nails, and skin.
• Trichophyton erinacei: This species is found in hedgehogs and can cause infections in humans who come into contact with infected animals. It is known to cause infections in the scalp, nails, and skin.
• Trichophyton ajelloi: This species is primarily found in soil and can cause infections in humans who come into contact with contaminated soil. It is known to cause infections in the skin and nails.

Pathogenesis of Trichophyton spp

• Adhesion to the skin or hair: Trichophyton spp. can adhere to the epidermis or hair via a variety of mechanisms, including:
  • Secretion of adhesive proteins: Trichophyton spp. are capable of secreting a variety of adhesive proteins that aid in their attachment to the surface of the epidermis or hair. These proteins are capable of binding to specific cell surface receptors.
  • Production of pili: Trichophyton spp. are also capable of producing pili, which are tiny, hair-like structures that help the fungus attach to surfaces. Pili are composed of the same protein as epidermis and hair, keratin.
• Invasion of the keratinized tissue: Once Trichophyton spp. have adhered to the epidermis or hair, they are able to invade keratinized tissue. This is accomplished through the production of keratinolytic enzymes, which degrade the keratin found in epidermis and hair. The fungus produces keratinolytic enzymes that can degrade keratin into smaller molecules that can be absorbed by the fungus.
• Production of keratinolytic enzymes: Trichophyton spp. are capable of producing numerous keratinolytic enzymes, including:
  • Proteases: Proteins are broken down into smaller molecules by proteases. Trichophyton spp. are capable of producing numerous proteases that degrade keratin.
  • Lipases: Lipases are enzymes that degrade lipids into smaller molecules. Trichophyton spp. are capable of producing lipases that can degrade the lipids that compose the epidermis and hair cell membranes.
• Evasion of the immune system: Several mechanisms allow Trichophyton spp. to elude the immune system, including:
  • Production of antigens that are similar to human antigens: Trichophyton spp. are capable of producing human-like antigens. This can hinder the immune system’s ability to differentiate between the fungus and the host cells.
  • Production of enzymes that break down immune cells: Trichophyton spp. are capable of producing enzymes that are able to degrade immune cells. This can aid the fungus in avoiding immune system destruction.
  • Upregulation of genes that promote fungus growth: Trichophyton spp. are capable of upregulating genes that promote fungus growth. This can facilitate the growth and spread of the fungus despite the presence of the immune system.

Clinical Manifestations of Trichophyton spp infections

The clinical manifestations of Trichophyton spp. infections can vary depending on the fungus species and infection site. Nonetheless, typical symptoms include:

• Ringworm: Multiple species of Trichophyton, including T. rubrum, T. mentagrophytes, and T. tonsurans, are responsible for ringworm. T. rubrum causes the most prevalent form of ringworm. Ringworm can affect any region of the body, but scalp, face, and legs are the most common sites.
• Athlete’s foot: Athlete’s foot is caused by the fungi T. rubrum and T. mentagrophytes. It is typically caused by strolling barefoot in moist areas, such as locker rooms and swimming pools. Athlete’s foot can be an infection that recurs.
• Jock itch: Jock rash is caused by the fungi T. rubrum and T. mentagrophytes. It is typically caused by sweating and friction in the groin area and is most prevalent in males. It is possible for jock rash to be a recurrent infection.
• Tinea capitis: Tinea capitis is caused by a number of distinct Trichophyton species, including T. tonsurans, T. violaceum, and T. megynii. It is most prevalent in minors and is commonly transmitted through contact with infected humans or animals. If left untreated, tinea capitis can induce permanent hair loss.
• Onychomycosis: Onychomycosis is caused by a number of distinct Trichophyton species, including T. rubrum, T. mentagrophytes, and T. tonsurans. It is most prevalent among adults and is typically transmitted through contact with infected people or objects. If left untreated, onychomycosis can cause permanent nail injury.
• Cellulitis: Cellulitis is a bacterial cutaneous infection that can develop around an infection with Trichophyton spp. The affected area is characterized by redness, edema, pain, and heat.
• Impetigo: Impetigo is a bacterial skin infection that can develop in infants with scalp infections caused by Trichophyton spp. It manifests as small, crusty sores on the epidermis.
• Sepsis: Sepsis is a severe bloodstream infection that can develop. Symptoms include fever, chills, rapid respiration, and confusion.

Treatment of Trichophyton spp infections

Infections caused by Trichophyton spp. are treated according to the type of infection and the severity of the symptoms. Antifungal topical creams or ointments are frequently used to treat moderate Trichophyton infections. Antifungal oral medications may be prescribed for more severe infections.

The following are some of the most frequently used oral antifungal medications for treating Trichophyton spp. infections:

• Griseofulvin
• Itraconazole
• Terbinafine
• Ketoconazole
• Fluconazole

Prevention and Control of Trichophyton spp infections

• Avoid contact with individuals who are infected. This includes avoiding skin, hair, and nail contact with them.
• Maintain the affected area’s cleanliness and dryness. This will assist in preventing the spread of the fungus.
• Always wear shoes in public. This will prevent the infection from spreading to your feet from contaminated surfaces.
• Use a different towel to clean the afflicted area. This will prevent the infection from spreading to other parts of your body.
• Regularly wash bedding and apparel. This will aid in the elimination of any fungus that may be present on these objects.
• Consult a physician for Trichophyton spp. infection treatment. The treatment will prevent the infection from spreading and alleviate your symptoms.
• Do not share personal items with others, including combs, brushes, and towels.
• Keep your fingernails brief. This will prevent fungus from sprouting beneath your nails.
• Take a daily shower or bath. This will aid in the removal of any cutaneous fungus that may be present.
• Utilize an antifungal washcloth or detergent. This will assist in eliminating any fungi that may be present on your epidermis.
• Consult a physician if you have a rash or other skin condition. Early treatment can aid in preventing the infection’s spread.
• Avoid going barefoot in locker rooms, restrooms, and swimming pools.
• Do not touch an infection if you have one. This can cause the disease to proliferate.
• Apply an antifungal salve or ointment according to your doctor’s instructions.
• Take antifungal medication orally as prescribed by your physician.

Laboratory Diagnosis of Trichophyton spp infections

The laboratory diagnosis of Trichophyton spp. infections typically involves one or more of the following methods:

• Microscopic examination: A sample of skin, hair, or nail is taken and examined under a microscope for the presence of fungal elements such as hyphae, spores, or arthroconidia. The sample can be stained with special dyes such as potassium hydroxide (KOH) or calcofluor white to enhance the visibility of the fungal elements.
• Culture: A sample of skin, hair, or nail is taken and cultured on a special fungal medium such as Sabouraud agar. The culture is observed for the growth of Trichophyton spp. colonies, which can take up to 2-4 weeks.
• Molecular methods: Polymerase chain reaction (PCR) and DNA sequencing can be used to identify the specific species of Trichophyton spp. based on the genetic material present in the sample.
• Skin biopsy: In some cases, a small sample of skin tissue may be taken and examined under a microscope or cultured to diagnose a Trichophyton spp. infection.

FAQ

References

1. Kishore, K., Roy, P., & Sardana, K. (2018). Diagnosis and management of dermatophyte infections. Indian journal of dermatology, 63(4), 277–287. https://doi.org/10.4103/ijd.IJD_443_17
2. Singh, A., Masih, A., Khurana, A., Singh, P. K., Gupta, M., & Hagen, F. (2017). Molecular and phenotypic characterization of dermatophytes isolated from dermatophytosis patients in Delhi, India. Medical mycology, 55(3), 248–256. https://doi.org/10.1093/mmy/myw072
3. Vu LT, Duc NM, Tra My TT, Bang LV, Luu DT, Thong PM. The first case of Trichophyton spp. pneumonia reported in Vietnam. Respir Med Case Rep. 2021 Feb 18;32:101371. doi: 10.1016/j.rmcr.2021.101371. PMID: 33680802; PMCID: PMC7910523.
4. https://en.wikipedia.org/wiki/Trichophyton
5. http://en.fungaleducation.org/trichophyton-spp/