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,
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.
Depending on what
your stool is being tested for, you may only need to collect one stool sample,
or you may need several stool samples over a period of days.
A stool culture is done to:
No special preparation is required
before having this test. Tell your doctor if you have recently taken
antibiotics, traveled out of the country, or
had a recent test with
contrast material, such as a barium swallow or a barium enema.
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?).
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:
Take the sealed container to your doctor's office or the
laboratory as soon as possible. You may need to deliver your sample to the lab
within a certain time. Tell your doctor if you think you may have trouble
getting the sample to the lab on time.
You may need to collect
several stool samples over 7 to 10 days if you have digestive symptoms after
traveling outside the country.
Samples from babies and young
children may be collected from diapers (if the stool is not contaminated with
urine) or from a small-diameter glass tube inserted into the baby's rectum
while the baby is held on an adult's lap.
Sometimes a stool sample
is collected using a rectal swab that contains a preservative. The swab is
inserted into the rectum, rotated gently, and then withdrawn. It is placed in a
clean, dry container and sent to the lab right away.
Collecting a stool sample does not
normally cause any discomfort.
If your doctor collects the stool
sample using a cotton swab, you may feel some pressure or discomfort as the
cotton swab is inserted into your rectum.
There is no chance for problems while collecting
a stool sample. Be sure to wear gloves when you collect the sample and wash
your hands before and after you collect the sample. This will help protect you
from spreading an infection.
A stool culture is done to identify
bacteria, viruses, or fungi that may be causing an infection. Stool
culture test results usually take 2 to 3 days. But some cultures for fungus may take weeks to get results.
No disease-causing (pathogenic) bacteria, fungi, or viruses are present or grow in the culture.
Bacteria (such as
salmonella, shigella, campylobacter, certain types of
Escherichia coli[E. coli], or
Yersinia enterocolitica) grow in the culture. Fungi such as yeast are found in the stool.
If bacteria are found in the culture,
sensitivity testing may be done to help choose the
The stool also may be examined under a microscope to look for parasites such as Giardia.
Reasons you may not be able to
have the test or why the results may not be helpful include:
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
March 7, 2012
Adam Husney, MD - Family Medicine
& Jerome B. Simon, MD, FRCPC, FACP - Gastroenterology
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