Understanding Your Laboratory Test: What to Expect

This test is a laboratory analysis that measures substances in a sample of your blood, urine, or other body fluid to help your doctor evaluate how well your body is functioning.

A stool bacteria culture test, also called a stool culture or bacterial culture of stool, is a laboratory test that identifies harmful bacteria in your feces. The test works by placing a small stool sample on special growth materials (culture media) that allow bacteria to multiply. Lab technicians then examine the grown bacteria under a microscope and perform additional tests to identify exactly what type of bacteria is present.

Your doctor may order this test to help diagnose a medical condition, monitor an ongoing illness, check how well a treatment is working, or screen for possible health problems before symptoms appear.

Your doctor may order this test if you have symptoms of a bacterial gastrointestinal infection, such as diarrhea (especially if bloody), abdominal pain, cramping, nausea, vomiting, or fever. Common bacterial infections this test can detect include Salmonella, Shigella, Campylobacter, Escherichia coli O157:H7 (E. coli), and Yersinia. The test helps confirm whether your symptoms are caused by a bacterial infection and identifies the specific bacteria so the right treatment can be prescribed.

In general, you may be asked to avoid eating or drinking for a certain number of hours before your appointment, and you should tell your care team about all medicines, vitamins, and supplements you take.

Before the test, inform your doctor about any recent antibiotic use, antidiarrheal medications, or contrast dyes (like those used for CT scans or barium X-rays), as these may affect test results. You do not need to fast before providing a stool sample. It is important to collect the sample in a clean, dry, wide-mouthed container provided by your healthcare facility or laboratory. Avoid contaminating the sample with urine, toilet water, or toilet paper.

A trained health professional will collect the sample, usually by drawing a small amount of blood from a vein in your arm with a sterile needle, and the specimen is then sent to a laboratory for analysis.

Collect a small amount of stool (about 1-2 tablespoons or the size of a walnut) from a bowel movement. Ideally, collect the sample from a part of the stool that appears bloody, mucousy, or watery, as these areas are more likely to contain pathogens. Place the sample in the sterile container provided, close it tightly, and label it with your name and the date. Deliver the sample to the laboratory as soon as possible, preferably within 2 hours of collection. If you cannot deliver the sample immediately, store it in a refrigerator (not frozen) but do not keep it longer than 24 hours.

Your results are compared with standard reference ranges, and your doctor will explain whether your values fall within the normal range and what any abnormal findings may mean for your health and treatment plan.

Results are typically reported as either 'No pathogens isolated' (normal) or by naming the specific bacteria found. A positive result means a disease-causing bacterium was identified and is likely causing your symptoms. Your doctor will interpret the results in context with your symptoms, medical history, and other test results. If bacteria are found, the laboratory may also perform antibiotic susceptibility testing to determine which antibiotics will be most effective in treating the infection.