Infectious Disease and Microbiology – Epidermophyton floccosum

Overview

Epidermophyton floccosum is a dermatophyte mold that causes superficial fungal infections of keratinized tissues. It is an important cause of tinea (dermatomycosis) worldwide.

Unlike some other dermatophytes, E. floccosum typically infects skin and nails but not hair, which helps explain why it does not cause tinea capitis.

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Microbiologic Characteristics

Epidermophyton floccosum is a filamentous fungus characterized by:

• Septate hyaline hyphae

• Growth as a mold

• Dermatophyte behavior with affinity for keratinized tissues

It primarily involves the stratum corneum and nails.

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Epidemiology

E. floccosum is a common cause of dermatophyte infection worldwide.

Transmission is generally associated with contact with infected skin, contaminated surfaces, clothing, towels, or other fomites.

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Clinical Infections

E. floccosum causes superficial dermatophyte infections of the skin and nails.

Important manifestations include:

• Tinea cruris

• Tinea corporis

• Tinea pedis

• Inguinal dermatophytosis

• Onychomycosis

A major distinguishing feature is that it generally does not cause tinea capitis.

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Tinea Cruris

Tinea cruris involves the groin and upper medial thighs.

Typical findings may include:

• Pruritic erythematous plaques

• Scaling

• Well-defined advancing borders

• Central clearing

E. floccosum is an important dermatophyte associated with this syndrome.

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Tinea Corporis

Tinea corporis is dermatophyte infection of glabrous skin.

Lesions are often:

• Annular

• Scaly

• Pruritic

• Expanding outward with a more active border

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Tinea Pedis

Tinea pedis affects the feet and may present with:

• Interdigital scaling and fissuring

• Plantar scaling

• Pruritus

• Maceration

E. floccosum is one of the dermatophytes capable of causing this infection.

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Onychomycosis

E. floccosum can also infect the nails and produce onychomycosis.

Affected nails may become:

• Thickened

• Discolored

• Brittle

• Irregular or dystrophic

Nail infection generally requires a longer course of therapy than localized skin disease.

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Why Tinea Capitis Is Absent

A useful distinguishing feature is:

Epidermophyton floccosum infects skin and nails, but not hair

Therefore:

Tinea capitis is not a typical infection caused by this organism.

This helps distinguish Epidermophyton from dermatophytes in the genera Trichophyton and Microsporum.

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Diagnosis

Diagnosis is based on demonstrating the fungus in appropriate clinical specimens.

Specimens may include:

• Skin scrapings

• Nail material

The organism can be identified by:

• Direct microscopic examination

• Fungal culture

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Microscopy

Direct examination of infected keratinized material may reveal:

Septate hyaline fungal hyphae

This supports the diagnosis of dermatophytosis.

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Culture

Growth in fungal culture allows identification of the dermatophyte and can help distinguish E. floccosum from other causes of tinea.

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Treatment – Extensive or Inflammatory Disease

For extensive or inflammatory manifestations, the source recommends:

Itraconazole 200 mg orally daily for 2–4 weeks

Systemic treatment is generally more appropriate when disease is widespread or difficult to manage with topical therapy alone.

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Treatment – Localized Disease

For localized, noninflammatory infection, the source recommends topical:

Ciclopirox olamine, applied approximately every 12 hours.

Localized dermatophyte infections are commonly treated with topical antifungal agents.

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Onychomycosis Treatment

For nail infection, the source recommends:

Itraconazole 200 mg orally daily for 3–6 months

The prolonged duration reflects the slow growth of nails and difficulty eradicating fungi from the nail plate.

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High-Yield Clinical Pattern

Pruritic scaly dermatophyte infection

Skin or nail involvement

No hair infection

→ Think Epidermophyton floccosum

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Dermatophyte Comparison

Epidermophyton

→ Infects skin and nails

→ Does not infect hair

Trichophyton

→ Can infect skin, hair, and nails

Microsporum

→ Typically infects skin and hair, but not nails

This tissue tropism is a useful exam distinction.

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Exam Essentials

Organism: Epidermophyton floccosum

Type: Dermatophyte mold

Hyphae: Septate, hyaline

Distribution: Worldwide

Main infections: Tinea cruris, corporis, pedis, and onychomycosis

Hair involvement: Absent

Tinea capitis: Not typical

Diagnosis: Direct fungal examination + culture

Localized disease: Topical antifungal therapy

Extensive/inflammatory disease: Systemic itraconazole may be used

Onychomycosis: Requires prolonged systemic treatment

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Key clinical pearl: Epidermophyton floccosum infects skin and nails but not hair, so it can cause multiple forms of tinea and onychomycosis, but not tinea capitis.