Dermatophytes

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 invasion of the dermis and subcutaneous tissues are rare.
• Dozens of species within 3 genera: T. rubrum is the most common organism, but microbiology of infection varies by geographic locale and exposure history.
  • Trichophyton (e.g. T. rubrum, T. interdigitale, T. mentagrophytes and T. tonsurans)
  • Microsporum (e.g. M. canis)
  • Epidermophyton (E. floccosum).
• 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), 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.