Why Is a KOH Test Gram Conducted?

Submitted by Nic on October 18, 2012

KOH is the chemical formula used for potassium hydroxide. The KOH test gram is used to identify fungi by means of using a culture to dissolve human cells in it. This test helps to check if there is any fungal infection caused to our hair, skin or nails. The method of using to test identify or detect fungi was discovered by Hans Christian Gram. He was a Danish doctor and first accidentally examined a person's lung tissue cells that had died of pneumonia. Gram stain is a way of segregating one large group of bacteria into two; mainly, positive and negative. The Koh is used as a simple and most effective way to confirm gram stain. A few drops are put on the cells, the once that change color are gram negative while the ones that retain their color are positive. Most of the KOH test gram-negative bacteria are pathogenic which help in identifying the infections.

A sample of the infected area is taken and Potassium hydroxide is applied to it and is placed under the microscope to be analyzed. The koh test Gram follows a particular procedure. In this procedure a slide with a bacterial smear is first placed on a staining rack after this a few drops of KOH are added and left a minute or two. This is then analyzed if the color changes. The major shortcoming of the Gram staining technique is the tendency of some gram-positive bacteria to decolorize more readily than others, often resulting in these bacteria being perceived incorrectly as gram negative. Some factors, for example, composition of the growth medium and the age of the culture, can influence the tendency of gram-positive bacteria to decolorize. In koh test gram positive, the color of dark crystal violet is retained by the outer layer of the cell which is a thick layer of peptidoglycan. As compared to gram positive, the koh test gram negative bacteria do not retain the color and the pink safranin contradict stain stains the peptidoglycan layer. A negative koh test or normal test result means the person does not have a fungal infection.

Whereas the person with a positive test result means Dermatophytes or yeast are present and hence has a fungal infection. Dermatophytes are easily noticeable under the microscope by their long branch-like structures and yeast cells look round or oval. The KOH test may medically be covered under your insurance policy. Also check with your doctor in case your test is positive for treatment.

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