Fungal Culture Test: Uses, Procedure, Results - Verywell Health

A fungal culture test is a gold standard when it comes to diagnosing a fungal infection. There are millions of types of fungi, but only certain varieties can cause infections in people.

Fungi can include molds and yeasts, many of which occur naturally in and on the human body. There are some situations, like a weakened immune system, that could lead to an overgrowth of these fungi. When this happens, you can develop superficial infections on your skin or nails, or even a systemic infection that can affect your entire body.

This article will review what types of fungi cause infections, what those infections might look like, and how a fungal infection is diagnosed.

Mr. Yu / Getty

What Are Fungal Infections?

Fungi are everywhere around us—in the air we breathe, in the soil, and even in our own skin. There are many types of fungi, including molds, yeasts, and even mushrooms. Some of these fungi are useful, but about half of them can cause disease in people if they are allowed to grow out of control.

Superficial Fungal Infections

A superficial fungal infection is a term used to describe a fungal overgrowth that only affects the outer, or superficial layers of your body like your skin, genitals, and nails. These are the most common types of fungal infections.

Examples of superficial fungal infections include:

Systemic Fungal Infections

A systemic fungal infection is one that affects the organ systems within your body. These infections can be serious and even life-threatening. People who have weakened immune systems from certain conditions or medications are most at risk for these infections, but they are also common in people who work with soil, plants, and animals.

Some systemic infections develop as a result of out-of-control superficial infections, but you can also develop these infections from direct exposure. Certain types of fungi release tiny spores that are released into the air. If you breathe in these spores, fungal infections can settle into your lungs, causing problems like fungal pneumonia. This is a common complication for people living with HIV/AIDS.

Uses of a Fungal Culture Test

While quicker methods are used to diagnose common fungal infections like ringworm or athlete's foot, a culture of scrapings from the affected area is a tool to diagnose the type of fungi present.

Cultures are tests that use a container and some type of material that can support the growth of things like fungi and bacteria. A sample of fluid or tissue is placed on this material, which offers ideal growing conditions. This means if bacteria or fungi exist in the sample being tested, they will continue to grow on the culture material.

In addition to confirming the presence of a fungal infection, a culture can also help your healthcare provider identify exactly which type of fungi is causing your infection. Cultures can be used to diagnose both superficial and systemic fungal infections and can help your healthcare provider tailor your treatments to fight that particular type of fungi.

Why Do I Need a Fungal Culture Test?

Some fungal infections can be treated with over-the-counter powders, creams, and ointments. If you are prone to superficial fungal infections like athlete's foot, you may be able to diagnose and treat an infection yourself. However, if your symptoms get worse or don't go away in a matter of weeks, you may need to see a healthcare provider for more intensive treatment.

A fungal culture will help your healthcare provider identify the specific type of fungi causing your infection, tailor your treatments, or see if current treatments are working.

Symptoms of a Superficial Fungal Infection

Superficial fungal infections rarely cause serious illness, but they can be uncomfortable and annoying. Symptoms of these types of infections can include:

Symptoms of a Systemic Fungal Infection

Systemic infections are infections that develop internally and can impact your entire body. These infections tend to be more serious, especially for people with weakened immune systems. These are sometimes called opportunistic infections because they occur when a common fungi or bacteria overtake a body in a weakened state.

Symptoms of systemic fungal infections can include things like:

• Fever
• Muscle ache
• Headache
• Chills
• Nausea
• Changes in your heart rate

Fungi That Can Cause Infections

Some fungi are more common than others, and the list below outlines some types that can cause infection in humans.

• Tinea: This is a group of diseases caused by fungus. There are several specific causes and varieties of tinea infection, but the most common include ringworm and athlete's foot. Tinea infections are usually superficial and are rarely severe.
• Candidiasis: Candida infections are caused by types of yeast that occur naturally in and on the body. Candida albicans are the most common of these. However, when these yeasts have the opportunity to grow out of control, often because of environmental factors or a weakened immune system, they can cause superficial infections and even serious systemic infections. These yeasts formally live on human skin, in the mouth, in genital areas, and the gastrointestinal tract. Examples of these types of infections can include vaginal yeast infections and thrush.
• Cryptococcus neoformans: This infection is caused by a type of fungus that lives in the soil, animal droppings, and other organic materials like decaying wood. While these infections are not contagious, they are spread through tiny spores that you might breathe in if you are exposed. These spores don't cause a problem for most people, but people with weakened immune systems are likely to develop infections.
• Blastomycosis: This is an infection caused by fungi called blastomyces that live in the environment. Organic materials like moist soil and decomposing leaves and wood are common locations for this fungus, which can be found across the United States and Canada. These fungi cause infection, particularly in people with weak immune systems, when spores from the fungi are inhaled.
  
• Aspergillosis: This fungal infection is caused by a common mold found indoors and outdoors. Most people can breathe in these fungi every day with no problem, but for some people—like those with weak immune systems or lung diseases—these fungi can cause severe infection. The lungs are a common target for infection with this type of fungi.
• Histoplasmosis: These infections are caused by histoplasma, a type of fungus found mostly in bird and bat droppings. Like other types of environmental fungi, these are most harmful when people with weakened immune systems inhale the spores. Histoplasma can be found in the United States, Central, and South America, Asia, Africa, and Australia.
• Coccidioidomycosis (Valley Fever): This type of fungus is found in the soil and dust in parts of the United States, Mexico, and Central and South America. Breathing in the spores of these fungi can lead to infection, mostly in people with weakened immune systems.

What to Expect During a Fungal Culture Test

Fungal infections can occur just about anywhere on the body, so how a fungal culture is done can be very different from one person to another.

When a fungal culture is done, your healthcare provider must take a sample of fluid, tissues, or cells from your body to place in the culture dish or some other type of testing field. Below is a list of common testing or collection techniques and the type of fungal infection they are used to detect.

• Nail or skin scraping: Your healthcare provider will scrape bits of your nail or skin for testing to diagnose skin and nail fungal infections.
• Swab test: A swab is used to gather tissue or fluid from areas like the genitals and the mouth. This is often used to diagnose infections like thrush and vaginal yeast infections.
• Blood culture test: This test looks for systemic fungal infection by culturing a sample of a blood draw from one of your veins.
• KOH Prep: This test is sometimes used interchangeably with skin scraping and uses a collection of cells placed under a microscope with a potassium hydroxide solution.
• Urine test: The culture is done using a urine sample, usually to help diagnose a vaginal yeast infection.
• Sputum culture: A sputum culture is done by collecting the thick mucus you may bring up with a cough. This is different from spit or saliva, and may also be collected with a procedure called a bronchoscopy.

How to Prepare

There is little to no preparation involved on your part when it comes to having a fungal culture done. If your symptoms are in a difficult-to-reach area, you may want to wear clothing that is easy to remove when you arrive for testing.

Do Home Tests Work?

Several companies make at-home tests to identify the presence of a fungal infection, and some people believe you can even detect fungi in your saliva by spitting into a cup. While these tests are easy and convenient and may signal the presence of some type of fungi or yeast, they don't provide much information in the way of how much fungus is in your body, or what type is causing your symptoms.

Risks and Side Effects

Risks and side effects from fungal cultures are minimal. You may have some discomfort during a swab or sputum culture, and a blood culture collection could leave you with some soreness and bruising where your vein was accessed.

Otherwise, the biggest risk can come from a skin scraping but could result in light bleeding, pain, or inflammation for a short period after the test is done.

Summary

Your healthcare provider may be able to diagnose your rash or other surface irritations simply by examining the area, but culture is the gold standard when it comes to accurately diagnosing fungal infections. A culture uses a sample of cells or tissue to look for fungal growth. This test can help your healthcare provider identify the specific type of fungus that is causing your infection.

A Word From Verywell

If you are experiencing rashes or irritation that could be caused by a fungus, your healthcare provider may want to do a fungal culture to confirm a diagnosis. Fungal cultures are not very invasive, and there are few risks to worry about. Having this test done can help your healthcare provider tailor your treatment to help you get relief faster.

Frequently Asked Questions

• It depends on what type of culture is being done. A KOH test may show results quickly, but other types of cultures can take up to a few days.

• Fungal cultures are the gold standard when it comes to diagnosing fungal infections. Not only can this test detect the presence of a fungal infection, but it can also be used to identify the specific type of fungi causing the problem.

• How your fungal culture is done will depend on where you are having symptoms of a fungal infection. If you have a fungal infection on the skin, your healthcare provider may take a small scraping of skin cells for testing. To diagnose oral thrust or a vaginal yeast infection, a cotton swab is used to collect fluid and cells. Blood testing may also be done to help diagnose systemic infections.

• The specimen used for a fungal culture is essentially a sampling of cells from the affected area. This can be skin, nails, and even bodily fluids.