Fungal hyphae in KOH preparation of pus discharge in details

Fungal hyphae in KOH preparation of pus discharge

Fungal hyphae in KOH preparation of pus discharge

Fungal hyphae in KOH preparation of pus discharge at 40X objective under the microscope as shown above picture.

Principle of KOH preparation

As you know, potassium hydroxide (KOH) is a strong alkali. When specimens such as pus, skin, hair, nails or sputum mixes with, it softens, digests and clears the tissues i.e.  keratin present in skin surrounding the fungi so that the fungal elements( yeast, cell with pseudohyphae, budding, hyphae, granules, conidia etc.) of fungi can be seen under microscope.


1.  Equipment

  • Microscope

2. Reagent and laboratory wares

  • Glass Petri dishes
  • clean and grease free glass slide
  • Cove slip
  • Straight wire or bent wire
  • Needle
  • Bunsen burner
  • 20% KOH

3. Specimen

It may vary according to site of infections such as pus from draining sinus, aspirate from nasal sinuses, respiratory specimen, skin scrapings, nail clipping, hair, corneal scraping , material from ear discharge, etc. But, here we got pus discharge for KOH mount.


  1.  Emulsify the specimen in a drop of 20% KOH on a glass slide with the help of  inoculating loop.
  2. Apply gentle heat by passing the slide over a Bunsen burner for 3-4 times in case of 10% KOH.
  3. Cover the smear with the cover slip  and leave for 5-10 minutes.
  4. As soon as the specimen has cleared, examine the preparation microscopically focusing  the 10X and finally observation using  40X objectives with the condenser iris diaphragm closed sufficiently to give a good contrast.


Observe for fungal elements in microscopy of the clinical specimens.

Result and Interpretation

  1. If there is presence of any fungal elements either yeast cells, cells with peudohyphae, budding, septate hyphae, aseptae hyphae, branching hyphae, conidia or granules etc. during examination, KOH mount is positive i.e. fungal elements seen.
  2. No fungal elements seen during in microscopy of the clinical specimen, KOH preparation is negative.
  3. Interpretation of results should do by critical analysis of the type, size and color of the fungal elements that will be different for different fungi. Fungal culture is necessary is necessary for the isolation etiological fungal agents.
  4. Above pictures has fungal hyphae in KOH preparation.

Application of KOH preparation

The uses of KOH wet mount preparation are as follows-

  1. It  is used for the rapid detection of fungal elements in clinical specimen, as it clears the specimen making fungal elements more visible during direct microscopic examination.
  2. It is very useful for the presumptive diagnosis of the type fungal infections.


  1. Medical Mycology. Editors:  Emmons and Binford, 2nd ed 1970, Publisher Lea and Febiger, Philadelphia.
  2. Rippon’s JW: Medical Microbiology. The pathogenic fungi and the pathogenic Actinomycetes. 3rd ed 1988 Publisher WB saunder co, Philadelphia.
  3. Clinical Microbiology Procedure Hand book, Chief in editor H.D. Isenberg, Albert Einstein College of Medicine, New York, Publisher ASM (American Society for Microbiology), Washington DC.
  4. A Text Book of Medical Mycology. Editor: Jagdish Chandar.  Publication Mehata, India.
  5.  Practical Laboratory Mycology. Editors: Koneman E.W. and G.D. Roberts, 3rd ed 1985, Publisher Williams and Wilkins, Baltimore.
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