A stool (feces) sample can provide doctors with valuable information about what's going on when a child has a problem in the stomach, intestines, or other part of the gastrointestinal (GI) system.
A stool culture helps the doctor determine if there's a bacterial infection in the intestines. A technician places small stool samples in sterile plastic dishes containing nutrients that encourage the growth of certain bacteria. The targeted bacteria will only grow if they're already present in the stool sample. If bacterial colonies form, the technician evaluates them using a microscope and chemical tests to identify the organism.
A doctor may request a stool culture to look for illness-causing bacteria such as:
On occasion some other illness-causing bacteria may be noted.
The stool culture might be ordered if your child has diarrhea for several days or has bloody diarrhea, especially if there's been an outbreak of foodborne illness in your community, your child has recently eaten undercooked meat or eggs or unpasteurized milk, or your child has recently traveled to certain places outside the United States.
Unlike most other lab tests, a stool sample is usually collected by parents at home, not by health care professionals at a hospital or clinic. No special preparation is required, but tell your doctor if your child has recently taken antibiotics.
The doctor or hospital laboratory will usually provide written instructions on how to collect a stool sample. If instructions aren't provided, here are tips for collecting a stool sample from your child:
When the sample arrives at the laboratory, a technician smears stool samples on a growth-encouraging substance inside sterile plates. These plates are each kept at a temperature that ensures the quickest growth of targeted bacteria.
If no bacterial colonies form, the test is negative, meaning that there's no sign of a bacterial infection. But if bacterial colonies do form, the technician examines them under a microscope and may perform chemical tests to identify them more specifically.
In general, the result of the stool culture is reported within 24 to 48 hours.
No risks are associated with collecting stool samples.
Collecting a stool sample is painless. Tell your child that collecting the stool won't hurt, but it has to be done carefully. A child who's old enough might be able to collect the sample alone to avoid embarrassment. Tell your child how to do this properly.
If you have questions about the stool culture, speak with your doctor.