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Stool Culture

Does this test have other names?

Stool test, stool sample

What is this test?

This test looks for bacteria, viruses, and other organisms in your stool. This test can help find out what's causing a digestive tract infection.

For this test, your stool sample is placed in a special container with the nutrients that bacteria or other organisms need to grow. The lab waits until enough organisms are present to be seen under a microscope. Once your doctor knows the type of organism causing your infection, he or she can diagnose and treat your illness.

Why do I need this test?

You may need this test if your doctor suspects that you have a digestive tract infection. Symptoms may include:

  • High fever

  • Stools that contain blood or mucus

  • Severe stomach pain or cramping

  • Severe diarrhea

  • Nausea

  • Diarrhea that lasts more than a few days

These symptoms are often caused by food poisoning. You can get food poisoning by eating food or drinking water that has been contaminated with bacteria, parasites, viruses, or other organisms. 

You may also need this test if you have immunity problems or if your white blood cell count is high, a sign that your body is trying to fight off an infection.

You may also need this test if you've traveled to a region where clean water is unavailable and you have symptoms of parasitic infection. You may also need this test if you have diarrhea that doesn't go away with treatment.

You may also need this test if you have taken broad-spectrum antibiotics or if you are an older adult. These factors can make it more likely that you will pick up a dangerous strain of bacteria, such as Clostridium difficile.

What other tests might I have along with this test?

Your doctor may also order other tests to help find out the bacteria or viruses causing your infection. These tests include:

  • Gram stain

  • Loeffler methylene blue stain

  • Blood culture

  • Blood tests, including a complete blood count, serum electrolyte assessment, blood urea nitrogen, or creatinine test

  • C. difficile test

Your doctor may also order tests to help rule out other conditions like a urinary infection or appendicitis. These tests include:

  • Viral antigen stool test

  • Urine culture

  • Abdominal ultrasound

  • Abdominal CT

  • Contrast enema

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Normal results are negative, meaning that no germs were found in your stool culture and that you don't have an infection.

Positive results mean that bacteria, parasites, or other germs were found in your stool culture and that they may be causing your stomach problems.

Sometimes the test shows a false-negative result, meaning that the test missed certain infectious bacteria. If you still have symptoms of infection, your doctor may order other tests to find out the cause of your stomach problems.

How is this test done?

This test requires a stool sample. Your doctor will instruct you how to collect a sample into a disposable specimen container with a lid. Don't collect fecal material from the toilet bowl or put toilet paper into the specimen container. Wear rubber or latex gloves when collecting the sample and be sure to wash your hands thoroughly afterward.

Does this test pose any risks?

This test poses no known risks.

What might affect my test results?

Other factors aren't likely to affect your results.

How do I get ready for this test?

You don't need to prepare for this test.  But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.