Fungal Culture for Fungal Nail Infections
A fungal culture is a test to find a fungus that can cause an infection.
Your doctor 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 added to a substance that promotes the growth of fungi. If no fungus grows, the culture is negative. If a fungus grows, the culture is positive. The type of fungus may be identified using a microscope or chemical tests. Sometimes other tests are done to find the right medicine for treating the fungal infection. This is called sensitivity testing.
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 medicine.
No fungal growth is present. But 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.
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
Although fungal cultures can identify the type of fungus infection, they are not routinely used because they take a long time and are expensive. Another type of culture test, called the dermatophyte test medium (DTM) culture, can tell if dermatophytes are present. The DTM culture costs less than a traditional fungal culture, can be done in a doctor's office, and gives results in 3 to 7 days.
If your culture is normal, your doctor may do other tests to determine the cause of the nail damage.