Dermatophytes

Dermatophytes is a topic covered in the Johns Hopkins ABX Guide.

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MICROBIOLOGY

  • Dermatophytes: filamentous fungi that colonize and digest keratinized structures such as the stratum corneum of skin, hair and nails.
    • Cause of superficial infections at those sites with local inflammation and damage.
    • Deeper invasions of the dermis and subcutaneous tissues are rare.
  • Dozens of species. T. rubrum is the most commonly isolated organism, but microbiology of infection varies by geographic locale and exposure history.
    • Trichophyton (e.g. T. rubrum, T. interdigitale, T. mentagrophytes, T. tonsurans, T. verrucosum)
    • Microsporum (e.g. M. canis, M. persicolor)
    • Epidermophyton (E. floccosum).
    • Other species: Arthroderma, Ctenomyces, Guarromyces, Lophophyton, Nannizzia, Paraphyton.
  • Certain species have a tendency for infection of specific structures:
    • Trichophyton--hair nails and skin
    • Microsporum--hair and skin
    • Epidermophyton--skin and nails.
  • Dermatophytes can also be classified according to usual habitat: anthropophilic (humans, e.g. T. rubrum, T. tonsurans, E. floccosum), zoophilic (cats, dogs, e.g. M. canis, T. verrucosum and M. persicolor), geophilic (soil, e.g. M. gypseum).
  • Acquisition of dermatophyte spores: can be via direct contact with a human or animal carrier, or indirectly from contaminated surfaces, including household items such as clothing, towels, bedding and combs
  • Terbinafine resistance in T. rubrum and T. interdigitale with associated clinical failure is an emerging problem in multiple countries, most notably in India.
  • Diagnostics (see more below)
    • Conventional methods such as culture, morphology, growth requirements, biochemical testing and direct microscopy are the mainstay of microbiological identification
    • Advanced methods: nucleic acid amplification (e.g. PCR), MALDI-TOF-MS,

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MICROBIOLOGY

  • Dermatophytes: filamentous fungi that colonize and digest keratinized structures such as the stratum corneum of skin, hair and nails.
    • Cause of superficial infections at those sites with local inflammation and damage.
    • Deeper invasions of the dermis and subcutaneous tissues are rare.
  • Dozens of species. T. rubrum is the most commonly isolated organism, but microbiology of infection varies by geographic locale and exposure history.
    • Trichophyton (e.g. T. rubrum, T. interdigitale, T. mentagrophytes, T. tonsurans, T. verrucosum)
    • Microsporum (e.g. M. canis, M. persicolor)
    • Epidermophyton (E. floccosum).
    • Other species: Arthroderma, Ctenomyces, Guarromyces, Lophophyton, Nannizzia, Paraphyton.
  • Certain species have a tendency for infection of specific structures:
    • Trichophyton--hair nails and skin
    • Microsporum--hair and skin
    • Epidermophyton--skin and nails.
  • Dermatophytes can also be classified according to usual habitat: anthropophilic (humans, e.g. T. rubrum, T. tonsurans, E. floccosum), zoophilic (cats, dogs, e.g. M. canis, T. verrucosum and M. persicolor), geophilic (soil, e.g. M. gypseum).
  • Acquisition of dermatophyte spores: can be via direct contact with a human or animal carrier, or indirectly from contaminated surfaces, including household items such as clothing, towels, bedding and combs
  • Terbinafine resistance in T. rubrum and T. interdigitale with associated clinical failure is an emerging problem in multiple countries, most notably in India.
  • Diagnostics (see more below)
    • Conventional methods such as culture, morphology, growth requirements, biochemical testing and direct microscopy are the mainstay of microbiological identification
    • Advanced methods: nucleic acid amplification (e.g. PCR), MALDI-TOF-MS,

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Last updated: September 2, 2021