Dermatophytes Overview

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Questions and Answers

What is the taxonomic classification of dermatophytes?

Dermatophytes belong to the phylum Ascomycota, class Eurotiomycetes, order Onygenales, and family Arthrodermataceae.

Describe the morphology of dermatophyte colonies.

Dermatophyte colonies can be powdery, velvety, cottony, or fluffy, and exhibit varying colors depending on the species.

What specialized structures are found in dermatophytes?

Dermatophytes feature specialized structures such as chlamydoconidia and spiral hyphae.

What is the significance of keratinase in dermatophytes?

<p>Keratinase is a virulence factor that allows dermatophytes to break down keratin, facilitating their growth and invasion.</p> Signup and view all the answers

What skin infections are commonly caused by dermatophytes?

<p>Dermatophytes are responsible for skin infections known as 'ringworm' or tinea.</p> Signup and view all the answers

What are the microscopic characteristics of dermatophytes?

<p>Dermatophytes typically exhibit septate hyphae, macroconidia, and microconidia.</p> Signup and view all the answers

Explain the term 'keratinophilic' in relation to dermatophytes.

<p>'Keratinophilic' refers to dermatophytes' affinity for keratin, as they thrive on keratin-containing tissues.</p> Signup and view all the answers

What is the primary habitat of dermatophytes?

<p>Dermatophytes primarily inhabit the skin, hair, and nails of humans and animals.</p> Signup and view all the answers

What is the range of genome sizes found in dermatophytes?

<p>The genome sizes range from 2.25 Mb to 24.1 Mb.</p> Signup and view all the answers

Describe the ploidy in E.floccosum's conidia and hyphae.

<p>E.floccosum has haploid conidia that are uninucleated and multinucleated hyphae.</p> Signup and view all the answers

What type of ecological classification do anthropophilic dermatophytes belong to?

<p>Anthropophilic dermatophytes live on humans.</p> Signup and view all the answers

Identify the colony appearance characteristics of E.floccosum.

<p>E.floccosum colonies are greenish-brown or khaki, have a suede-like surface, and may develop white tufts as they age.</p> Signup and view all the answers

What infections are caused by Epidermophyton floccosum?

<p>E.floccosum is known to cause Tinea pedis, Tinea cruris, Tinea corporis, and Onychomycosis.</p> Signup and view all the answers

What distinctive feature characterizes the macroconidia in E.floccosum?

<p>The macroconidia of E.floccosum are smooth and have thick walls.</p> Signup and view all the answers

How do the reverse pigments of E.floccosum colonies appear?

<p>The reverse pigments of E.floccosum colonies generally display a yellowish-brown color.</p> Signup and view all the answers

In what way is E.floccosum's growth behavior unique compared to other dermatophytes?

<p>Unlike other dermatophytes, E.floccosum does not invade hair in vivo.</p> Signup and view all the answers

What are chlamydospores and what role do they play in the survival of Epidermophyton floccosum?

<p>Chlamydospores are survival structures formed in older cultures that help Epidermophyton floccosum withstand adverse conditions.</p> Signup and view all the answers

What was the primary symptom observed in the 49-year-old woman with inflammatory tinea corporis?

<p>The primary symptom was nail lesions, particularly affecting the left big toe, which showed mild inflammation and thickening of the nail bed.</p> Signup and view all the answers

What diagnostic methods were used to confirm the presence of Epidermophyton floccosum in the patient's samples?

<p>Diagnostic methods included scraping scales from the affected nail for microscopic examination with 20% KOH and culturing samples on Sabouraud dextrose agar.</p> Signup and view all the answers

What specific cultural characteristics were noted in the colonies of Epidermophyton floccosum during the culture process?

<p>The colonies developed beige, velvety appearances, and microscopic analysis revealed septate hyphae and club-shaped macroconidia.</p> Signup and view all the answers

Describe the significance of using 20% potassium hydroxide (KOH) in the diagnosis of tinea unguium.

<p>20% potassium hydroxide (KOH) is used to clear keratin in nail samples, allowing for the visualization of fungal elements under a microscope.</p> Signup and view all the answers

What treatment options were recommended for the patient suffering from tinea unguium caused by Epidermophyton floccosum?

<p>Treatment included topical antifungals such as 8% ciclopirox and oral terbinafine at 250 mg as first-line therapy.</p> Signup and view all the answers

What does the absence of microconidia in Epidermophyton floccosum indicate regarding its morphological characteristics?

<p>The absence of microconidia indicates a specific morphological characteristic that differentiates E. floccosum from other dermatophytes.</p> Signup and view all the answers

How does prolonged use of closed shoes contribute to the risk of developing tinea corporis in the observed patient?

<p>Prolonged use of closed shoes creates a warm and damp environment that promotes fungal growth, increasing the risk of tinea corporis.</p> Signup and view all the answers

What are the characteristic colors and textures of colonies of Microsporum canis?

<p>Colonies appear yellowish to brownish with a granular to cottony surface.</p> Signup and view all the answers

Describe the structure of macroconidia found in Microsporum canis.

<p>Macroconidia are multiseptate with thick rough cell walls, typically clavate, fusiform, or spindle-shaped.</p> Signup and view all the answers

How were the skin lesions related to the case study of Tinea corporis caused by Microsporum canis identified?

<p>Numerous annular erythematous plaques developed across her body, especially on the face, neck, and trunk.</p> Signup and view all the answers

What method was used to confirm the presence of Microsporum canis in the dermatology case?

<p>Direct microscopic examination and fungal cultures confirmed the presence of Microsporum canis.</p> Signup and view all the answers

What treatment was administered to the family affected by Tinea corporis?

<p>The family was treated with itraconazole (200 mg/d) for 1 month.</p> Signup and view all the answers

What does the presence of patchy alopecia in pets suggest in the context of Tinea corporis?

<p>It suggests that pets may also be infected with Microsporum canis, contributing to the outbreak.</p> Signup and view all the answers

What is the significance of the random amplified polymorphic DNA (RAPD) analysis in this case?

<p>RAPD analysis confirmed that the five isolated strains were the same fungal species.</p> Signup and view all the answers

How long after completion of treatment did the skin lesions resolve in the case study?

<p>The lesions resolved three months after the completion of treatment.</p> Signup and view all the answers

What are the common skin lesions associated with M.canis infection?

<p>The common skin lesions include inflammatory, eczematous lesions with erythema and scaling.</p> Signup and view all the answers

What are the cultural characteristics of Trichophyton spp. colonies?

<p>Trichophyton spp. colonies appear white to cream in color, with a powdery to granular texture, and a reverse pigment that ranges from yellow-brown to reddish-brown.</p> Signup and view all the answers

Describe the key microscopic features of macroconidia in Trichophyton spp.

<p>Macroconidia in Trichophyton spp. are thin- or thick-walled, clavate to fusiform in shape, and may be borne laterally directly on the hyphae or on short pedicels.</p> Signup and view all the answers

How does the presence of microconidia differentiate Trichophyton from Epidermophyton?

<p>The presence of microconidia is a distinguishing feature of Trichophyton, as Epidermophyton lacks these structures.</p> Signup and view all the answers

What symptoms did the 4-year-old girl exhibit in the case study of Tinea Faciei caused by Trichophyton benhamiae?

<p>The girl exhibited an itchy, erythematous, and annular plaque on her right face.</p> Signup and view all the answers

What type of agar was used for culturing the suspected Trichophyton infection in the case study?

<p>Sabouraud's dextrose agar (SDA) was used for culturing the suspected Trichophyton infection.</p> Signup and view all the answers

What microscopy technique revealed filamentous and spiral hyphae in the case study?

<p>Lactophenol cotton blue staining revealed the filamentous and spiral hyphae.</p> Signup and view all the answers

What morphology of microconidia was observed in Trichophyton mentagrophytes according to the case study?

<p>Microconidia of Trichophyton mentagrophytes were observed in a grape-like arrangement, inserting laterally and terminally at the hyphae.</p> Signup and view all the answers

What was the confirmed cause of the tinea faciei in the presented case study?

<p>The tinea faciei was caused by the fungus Trichophyton benhamiae.</p> Signup and view all the answers

What two treatments were administered for the condition in the case study?

<p>Terbinafine (oral 125 mg/d) and sertaconazole nitrate cream (topical, twice daily) were the treatments given.</p> Signup and view all the answers

After 4 weeks of treatment, what was the outcome concerning the skin lesions?

<p>There was significant improvement in the skin lesions, with complete resolution of the plaque and residual erythema.</p> Signup and view all the answers

How was the diagnosis of tinea faciei established for the patient?

<p>The diagnosis was established through molecular sequencing tests that were consistent with reference strains of T.benhamiae.</p> Signup and view all the answers

What is the size of the annular plaque described in the case study?

<p>The annular plaque measured approximately 3 cm × 5 cm.</p> Signup and view all the answers

What symptoms were observed on the patient's face due to tinea faciei?

<p>The symptoms included an annular plaque with erythema covered with scales and crusts.</p> Signup and view all the answers

In which country was this case of tinea faciei caused by Trichophyton benhamiae first reported?

<p>The case was first reported in China.</p> Signup and view all the answers

What were the dosages for the oral and topical treatments used in the case?

<p>The oral treatment was 125 mg/d of terbinafine, and the topical treatment was sertaconazole nitrate cream applied twice daily.</p> Signup and view all the answers

Flashcards

Dermatophytes

Fungi that cause superficial skin infections.

Ringworm/Tinea

A common skin infection caused by dermatophytes.

Superficial and Cutaneous Mycoses

Infections that affect the outer layers of skin and hair.

Ascomycota

A phylum of fungi, which includes the order of dermatophytes.

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Keratinophilic Nature

Dermatophytes have a preference for keratin (a protein in skin).

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Keratinase

An enzyme produced by dermatophytes that breaks down keratin.

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Microscopic Characteristics

Dermatophytes have special structures like hyphae, macroconidia, and microconidia.

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Colony Morphology

Dermatophyte colonies have different appearances based on the species.

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Chlamydospores

Survival structures formed in older cultures of fungi, helping them withstand adverse conditions.

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Microconidia

Small, simple asexual fungal spores.Not produced by Epidermophyton floccosum.

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Macroconidia

Large, complex, asexual spores produced by fungi, often club-shaped.

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Epidermophyton floccosum

A specific fungus causing tinea unguium (nail infection) and other infections.

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Tinea unguium

A fungal infection of the nails.

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KOH test

A test using potassium hydroxide to examine fungal elements in nail scales.

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Sabouraud dextrose agar

A growth medium used to cultivate fungi.

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Septate hyphae

Fungal filaments with cross-walls separating cells. A characteristic of Epidermophyton floccosum.

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Genome size of dermatophytes

The size of the genome of a group of fungi varies from 2.25 Mb to 24.1 Mb

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Ploidy in dermatophytes

Dermatophytes can be haploid (uninucleated conidia) or multinucleated (in hyphae).

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Genomic conservation in dermatophytes

Dermatophyte genomes share a large number of orthologous genes (over 6000).

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Epidermophyton floccosum habitat

Epidermophyton floccosum is an anthropophilic dermatophyte (live on humans), found worldwide.

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E. floccosum growth rate

E. floccosum colonies grow slowly.

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E. floccosum colony color

E. floccosum colonies appear greenish-brown or khaki.

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Tinea infections caused by E.floccosum

Epidermophyton floccosum can cause athlete's foot, jock itch, ringworm and onychomycosis.

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Dermatophyte unifying characteristics

Dermatophytes share taxonomy, morphology, keratinophilic nature, genome, and habitat, which includes anthropophilic (human), zoophilic (animal), and geophilic (environment).

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Microsporum canis

A fungus that can cause skin infections, like ringworm

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Tinea corporis

A skin infection caused by fungi, characterized by itchy rashes.

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Colony appearance

The visual characteristics of a fungal colony, including color and texture.

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Macroconidia.

Large fungal spores, often multi-septate and have rough walls.

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Microconidia

Small fungal spores, typically single-celled and smooth-walled.

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Microscopic characteristics

Features of a fungus visible only under a microscope.

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RAPD

A molecular method to determine the similarity between different strains of fungus.

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Itraconazole

A medication used to treat fungal infections

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Trichophyton spp. Culture

Trichophyton species form colonies that are white to cream in color, powdery to granular in texture, and have a yellow-brown to reddish-brown reverse pigment.

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Trichophyton Macroconidia

These are thin- or thick-walled structures, often clavate or fusiform, which may grow directly on the hyphae or on short pedicels.

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Trichophyton Microconidia

Small, spherical, pyriform, or irregular structures, which help differentiate Trichophyton from other fungi. Found in grape-like arrangements.

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M.canis Infection

Infection often transmitted by exposure to symptomatic or asymptomatic cats/dogs, leading to inflammatory, eczematous lesions with redness and flaking.

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Tinea Faciei

A facial skin infection caused by Trichophyton, often with an itchy, red, ring-shaped patch.

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SDA Culture

Used for growing fungi, resulting in white colonies with a radiating, raised, and powdery margin, with a yellow-brown reverse.

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Lactophenol Cotton Blue Stain

A staining technique used to visualize hyphae and microconidia during fungal identification from tissue samples.

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Trichophyton benhamiae

A species of dermatophyte, which can cause facial ringworm.

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Tinea Faciei

A fungal skin infection affecting the face, characterized by an itchy rash.

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Trichophyton benhamiae

A specific type of fungus that causes tinea faciei.

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Molecular Sequencing Test

A test that identifies the specific type of fungus by analyzing its genetic material.

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Terbinafine (oral)

A medication taken by mouth used to treat fungal skin infections.

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Sertaconazole Nitrate Cream

A topical medication, applied to the skin, used to fight fungal skin infections.

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Annular Plaque

A ring-shaped skin lesion with redness, sometimes with scales and scabs.

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Complete Resolution

Full healing of the skin lesion.

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4 Weeks Treatment

A treatment period of 4 weeks was sufficient to clear up the rash.

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Study Notes

Dermatophytes

  • Dermatophytes are etiologic agents of skin infections, often called "ringworm" or tinea.
  • They cause superficial and cutaneous mycoses.
  •  Dermatophytes are classified in the phylum Ascomycota, class Eurotiomycetes, order Onygenales, and family Arthrodermataceae.

Unifying Characteristics

  • Taxonomy: Dermatophytes are categorized into various genera and species, including Trichophyton, Epidermophyton, Microsporum, and Nannizzia.
  • Morphology:
    • Colonies display diverse textures like powdery, velvety, cottony, or fluffy.
    • Colors vary based on species.
    • Microscopic characteristics include septate hyphae, macroconidia, microconidia, and specialized structures such as chlamydoconidia and spiral hyphae.
  • Keratinophilic nature: They have a preference for keratin.
  • Virulence factor: Keratinase is a virulence factor involved in keratin degradation.
    • Dermatophytes produce keratinases that break down keratin in infected tissues.
  • Genome: Genome size ranges from 2.25 Mb to 24.1 Mb.
    • Genome ploidy can vary, with conidia being uninucleated and hyphae, multinucleated.
    • Genome conservation includes over 6000 orthologs.
  • Habitat:
    • Anthropophilic: Live on humans.
    • Zoophilic: Live on animals.
    • Geophilic: Live in the environment.

Specific Dermatophyte Types

  • Epidermophyton floccosum: - Growth rate is slow.

    • Colonies appear greenish-brown or khaki with a suede-like texture.
    • Older colonies develop white, pleomorphic tufts of mycelium.
    • A yellowish-brown pigment often appears on the reverse side. - Microscopic features reveal septate hyphae, club-shaped macroconidia (thick walls), and lack microconidia.
    • A worldwide distribution, and it's anthropophilic, causing various infections like athlete's foot, jock itch, ringworm, and nail infections.

  • Microsporum canis:

    • Colony appearance includes yellowish to brownish colors, granular to cottony surface textures, and cream-colored to brown reverse pigment. - Microscopic features include both hyaline macroconidia and microconidia.
    • Macroconidia are multiseptate with thick walls and clavate or fusiform shapes, while microconidia are single-celled, smooth-walled, and mostly clavate.
    • Commonly associated with contact with cats or dogs, and often causes inflammatory, eczematous lesions with erythema and scaling.

  • Trichophyton:

    • Colony appearance varies from white to cream in color, with powdery to granular texture.
    • Reverse pigment can be yellow-brown to reddish-brown.
    • Microscopic characteristics include smooth-walled macro and microconidia.
    • Macroconidia can be thin or thick-walled, clavate to fusiform, and borne laterally on the hyphae. - Microconidia can be spherical, pyriform, or clavate.
    • Various infections can arise from contact with animals or surfaces.

  • Trichophyton benhamiae: This dermatophyte causes tinea faciei (facial ringworm).

    • Symptoms may include itchy, erythematous, annular plaques on the face.
    • Treatment usually involves antifungal therapy.

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