Fungal culture for fungal nail infections

Exam Overview

A fungal culture is used to find out whether fungi are present and, if so, what type of fungus it is.

Your health professional will collect a sample of skin and/or nail fragments (debris) under the infected nail. If a sample of debris cannot be removed, he or she will take a nail sample by lightly scraping the nail near the infected area or by using a small blade to shave off a piece of nail.

Nail or debris samples are placed on a jellylike substance (agar solution) and are checked for several weeks to see if any fungi grow. The type of fungus is then identified by using a microscope to look at the shape and pattern of the cells. It is also identified by the color of the cells when they are stained with special dyes.

Why It Is Done

A fungal culture will show whether a fungal nail infection is present and what type of fungus it is. A fungal culture is typically done when a diagnosis is unclear or when treatment of a fungal infection has not been successful. If uncommon fungi are identified, the infection can then be treated with different medication.

Results

Normal

No fungal growth is present. However, the test may be done again using more samples taken from other parts of the infected nail. This is because there may no longer be fungi on the edge of the infected area, where it is easiest to scrape for a sample, or in the dead tissue, even if you have a fungal nail infection.

Abnormal

Fungal growth is present, and the type of fungus is identified. Your treatment may depend on the type of fungus present.

What To Think About

If your culture is normal, your health professional may do other tests to determine the cause of the nail damage.

Although fungal cultures can identify the type of fungus infection, they are not routinely used because they take a long time and are expensive.

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Author:	Sabra L. Katz-Wise	Last Updated: August 23, 2006
Medical Review:	Patrice Burgess, MD - Family Medicine Randall D. Burr, MD - Dermatology
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