A stool culture is done to identify bacteria or viruses that may be causing an infection. Although more than 50 different kinds of bacteria normally live in the intestines, large numbers of abnormal bacteria, viruses, fungi, or parasites can grow in the intestines and cause infections and diseases.

For a stool culture, a stool sample is collected in a clean container and placed under conditions that allow bacteria or other organisms to grow. The type of infection is identified by noting the appearance of the growth, by performing chemical tests on the stool sample, and by looking at the sample under a microscope.

Usually several stool samples are collected over a period of days for accurate test results.

Why It Is Done

A stool culture is done to:

• Find the cause of symptoms, such as severe or bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever.
• Find and identify certain types of bacteria, viruses, fungi, or parasites that are causing infections or diseases, such as food poisoning, inflammation of the large intestine (pseudomembranous enterocolitis), cholera, and typhoid.
• Identify a person who may not have any symptoms of disease but who carries bacteria that can spread infection to others. This person is called a carrier. A person who is a carrier and who handles food is likely to infect others.
• Find out if treatment for an infection has been effective.

How To Prepare

No special preparation is required before having this test. Do not collect a stool sample if you have bleeding hemorrhoids. Women should not collect a stool sample during their menstrual period; wait until 3 days after your period has stopped. Tell your doctor if you have recently taken antibiotics, traveled out of your native country, or had a recent test with contrast material.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

Stool samples can be collected at home, in your doctor's office, at a medical clinic, or at the hospital. If you collect the samples at home, you may be given a special container.

You may need to collect more than one sample. Follow the same procedure for each sample.

Collect the sample as follows:

• Urinate before collecting the stool so that you do not get any urine in the stool sample. Do not urinate while passing the stool.
• Put on gloves before handling your stool. Stool can contain material that spreads infection. Wash your hands after you remove your gloves.
• Pass stool (but no urine) into a dry container. You may be given a plastic basin that can be placed under the toilet seat to catch the stool.
  • Either solid or liquid stool can be collected.
  • If you have diarrhea, a large plastic bag taped to the toilet seat may make the collection process easier; the bag is then placed in a plastic container.
  • If you are constipated, you may be given a small enema.
  • Do not collect the sample from the toilet bowl.
  • Do not mix toilet paper, water, or soap with the sample.
• Place the lid on the container and label it with your name, your doctor's name, and the date the stool was collected. If you are collecting more than one sample, use one container for each sample, and collect a sample only once a day unless your doctor gives you other directions.