Preparation and Procedure For Conducting a Stool Culture Test

Submitted on March 27, 2012

Stool culture is a stool test conducted to detect pathogenic bacteria in your gastrointestinal tract. This test is usually ordered when a person has been suffering from diarrhea for quite a few days and/or has blood or mucus in his/her stools.

Stool Culture Test

A stool culture test identifies the virus or bacteria that could be the cause of gastrointestinal infection.

The stool for the culture test needs to be collected in a clean, sterile container. This sample is then kept under conditions that allow bacteria to grow, thereby allowing for the possibility of detection of pathogenic bacteria.

Chemical tests are performed on the stool sample and observed under the microscope and the shape, size and color of the bacteria is noted to identify the type. Also, depending on what disease the doctor suspects, you may be required to collect one or more stool samples.

The sample collected shouldn't be contaminated with urine or water and once collected this sample needs to be taken to a lab within an hour. If that's not possible then it needs to be transferred into a vial or a container with a preservative and transported at the earliest. While collecting stool sample from infants, care needs to be exerted to ensure the stool is not contaminated with urine from the diaper or that the stool touches the diaper insides. Diapers have antibacterial substances that could inhibit bacterial growth in the stool culture test.


No specific preparation is required for this test. Only, you need to advise the doctor and the laboratory of any antibiotic medication you have taken recently. It would be sensible to wear gloves while collecting the sample, else wash hands thoroughly after collecting the sample, to avoid spread of infection, if any.

Urine cannot be a part of the stool sample. Therefore, urinate before you collect the stool sample.

Procedure to Conduct the Test

This is a standard stool test with no specific preparation or procedure. All you need to take care of is that you don't contaminate the sample. A stool culture test is often administered along with other tests like clostridium difficile toxin test, which helps find the cause of extended diarrhea or O&P test that identifies parasites. In a stool culture, the sample is smeared along with certain substances and incubated to encourage the growth of bacteria and other organisms. Any bacteria present in the stool will then begin to grow like colonies and will appear to be dots on the surface of the sample. As mentioned earlier, the shape, color and size of the bacteria helps differentiate the good bacteria from the bad.


You can obtain a result of a stool culture in two or three days. A normal stool culture test implies that no infectious or harmful bacteria, fungi or other organisms grew or were present in the sample. A normal result indicates that the test was negative.

An abnormal result means the test was positive and that the stool culture showed the presence or growth of infectious bacteria. Certain types of infectious bacteria and fungi include salmonella, Escherichia coli (E coli), shigella, Yersinia enterocolitica, campylobacter or parasites like Giardia lamblia.

Usually when bacteria are detected in the stool culture, doctors order a sensitivity test to determine the appropriate treatment.