Diagnostic Mycology Quiz

Diagnostic Mycology

• KOH Stain: Most commonly used stain for direct analysis of fungi.

• Histochemical Stains for Fungi:

  • Methenamine Silver: Highlights glycogen.
  • Periodic Acid Schiff: Used to detect certain fungal elements.

• KOH Stain Properties:

  • Clears fungal cell walls; alkali-sensitive.
  • Gentle heating can accelerate the reaction.
  • Used for direct examination of fungi.

• Negative Staining in Fungal Diagnosis: India Ink is used to highlight Cryptococcus neoformans in cerebrospinal fluid (CSF).

• Whitening Agents: Calcofluor White is a brightener used for fluorescing cellulose and chitin.

• Malignant Cell Detection: Papanicolaou Stain is used for examining secretion in the detection of malignant cells.

Differential Media

• Conversion Media for Dimorphic Fungi:

  • Cottonseed Conversion Agar converts Blastomyces dermatitidis from mold to yeast form.

• Aspergillus Differentiation Media:

  • Czapek’s Agar highlights all Aspergillus species in green mossy color.

• Standard Isolation Culture for Fungi:

  • Sabouraud’s Dextrose Agar is the standard for isolating fungal agents.

Aspergillus in Food Preservation

• Preservative Component: Aspergillus species utilize lactic acid in the preservation of bread.

Procedures and Conditions

• Blood Dilution in Broth Medium: Adding a minimum of 5 ml blood to broth results in a dilution of 1:10 to 1:20.

• CSF Collection: Must be collected aseptically via lumbar puncture, processed immediately, and not stored at room temperature.

• Storage Temperatures:

  • Hair, Skin Scrapings, and Tissue can be stored at room temperature.
  • Sputum must not be stored at room temperature.

• Fungal Cell Wall Components: Fungal cell walls typically contain chitin and ergosterol; however, peptidoglycan is not present.