Lab method
KOH preparation
Alkali clears keratin to reveal fungal elements
K-O-H prep
High-yield clue
Branching septate hyphae or 'spaghetti and meatballs' yeast on a KOH mount is the classic skin/nail fungal clue.
Overview
A wet-mount concept in which potassium hydroxide dissolves keratin and host cells so that fungal cell walls (hyphae, budding yeast, or spores) become visible under the microscope.
Classification
- Clearing agent concept
- Wet-mount light microscopy
- Fungal cell-wall visualization
- Non-specific method
Lab & identification clues
- KOH digests keratin and debris
- Hyphae and yeast walls resist alkali
- Pseudohyphae vs true hyphae vocabulary
- Often paired with calcofluor white for fluorescence
Associations
- Dermatophyte skin/nail study association
- Malassezia short hyphae and yeast pattern
- Candida pseudohyphae recognition
Commonly confused with
- Lactophenol cotton blue
- Gram stain
Frequently asked questions
What is KOH preparation?
A wet-mount concept in which potassium hydroxide dissolves keratin and host cells so that fungal cell walls (hyphae, budding yeast, or spores) become visible under the microscope.
What is the high-yield clue for KOH preparation?
Branching septate hyphae or 'spaghetti and meatballs' yeast on a KOH mount is the classic skin/nail fungal clue.
What is KOH preparation associated with?
KOH preparation is associated with Dermatophyte skin/nail study association, Malassezia short hyphae and yeast pattern, and Candida pseudohyphae recognition.
What is KOH preparation commonly confused with?
KOH preparation is commonly confused with Lactophenol cotton blue and Gram stain.
Original concept summary for coursework. Sources checked: OpenStax Microbiology 2e and NCBI Bookshelf Medical Microbiology; reviewed 2026-06. Describes vocabulary and interpretation concepts only; not a lab protocol and not for handling specimens or identifying patient isolates.