Dermatology Book

Fungal Infections

Viral Infection

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Fungal Culture

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  1. Indication
    1. Suspected fungal infection (KOH Preparation negative)
      1. Tinea Unguium
      2. Tinea Capitis
    2. Sensitivity to Antifungal Medications
  2. General
    1. Submit large amounts of debris
    2. Break up large pieces
    3. Collect in sterile urine cup
  3. Specimen collection
    1. Scaly Rash
      1. Collect scale as done in KOH Preparation
      2. Implant resulting scales on medium
    2. Non-Scaling Rash
      1. Wet cotton swab rubbed vigorously over lesion border
      2. Collect resulting debris into medium
    3. Nails
      1. Clip nails back to yellowish, crumbly portion
      2. Clip a sliver of crumbly portion and place on medium
      3. Gently scrape debris from under free edge of nail
    4. Scalp
      1. Gently scrub area with sterile toothbrush
        1. Tap toothbrush bristles on medium
      2. Scrape a few scales off scalp for culture
      3. Gently pluck short stumps of hair and place on medium
  4. Culture Medium
    1. Medium: Sabouraud's Peptone-Glucose Agar (most common)
    2. Additives: Dermatophyte test medium (DTM)
      1. Phenol indicator turns red when alkaline
      2. Poor sensitivity and Specificity
  5. Culture Identification
    1. Dermatophyte growth takes 2-4 weeks
      1. Minimum culture time to call negative: 21 days
    2. Keep culture bottle at room temperature
    3. Do not tightly cap bottles (loose enough to rattle)
      1. Dermatophytes are aerobes

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