Mycology: Laboratory Diagnosis of Fungi

Specimen Collection and Transport in Mycology

• Nail samples require scrapings or cuttings, cleaned with 70% isopropyl alcohol prior to collection.
• Blood and bone marrow specimens utilize a lysis centrifugation system and are collected in Brain Heart Infusion (BHI) broth.
• Hair sampling targets superficial and cutaneous mycoses while skin, blood, bone marrow, cerebrospinal fluid (CSF), and respiratory specimens are essential for systemic mycoses.
• Subcutaneous specimens can consist of abscess fluid, wound exudates, and tissues, as well as urogenital and fecal materials.

Cerebrospinal Fluid Collection

• CSF must be collected aseptically by a physician and transported immediately to the laboratory.
• Concentration through centrifugation is recommended before inoculation for accurate results.
• For Cryptococcus, one drop of concentrated sample may be examined microscopically using India ink or latex agglutination.

Hair Sampling Protocol

• Use sterile forceps to pull affected hair or cut it close to the scalp with sterile scissors.
• Place hair samples directly into a sterile petri dish.
• Inoculate onto fungal medium and incubate at room temperature (22°C to 30°C); fungi may show slow growth, typically taking 5-10 days.

Abscess Fluid and Wound Exudates

• Collect specimens aseptically from undrained abscesses using sterile needles and syringes.
• Tissues should be gently minced before inoculation onto culture media.

Respiratory Specimen Collection

• Collect respiratory specimens early in the morning, using sterile containers for transport.
• Examples include sputum, transtracheal aspirates, and pleural lavage fluid.

Urogenital Specimens

• Urine samples should be first-voided morning specimens, ideally collected through clean-catch or catheterized methods.
• Centrifuge urine and inoculate the resulting sediment.
• Vaginal and cervical specimens are collected using sterile swabs and placed into transport media.

Possible Fungal Pathogens by Body Site

• Blood may contain pathogens like Histoplasma capsulatum, Candida spp, Blastomyces dermatitidis, and Coccidioides immitis.
• CSF can show Histoplasma capsulatum, Candida spp, Coccidioides immitis, and Cryptococcus neoformans.
• Hair samples may reveal fungi from the Trichophyton and Microsporum genera.
• Nail infections may be attributed to Epidermophyton and Aspergillus among others.