Laboratory Blood Test: What It Is, How It Is Done, and What Your Results Mean

What is this test and why has my doctor ordered it?

The Bacteria #5 identified in Stool by Culture test is a laboratory examination that detects and identifies specific disease-causing bacteria in your stool sample. This test is part of a stool culture panel that can identify multiple types of harmful bacteria that may be causing gastrointestinal symptoms such as diarrhea, abdominal pain, nausea, or fever.

Why is this test performed and what information does it provide?

Your doctor may order this test if you have symptoms of a bacterial gastrointestinal infection, such as persistent diarrhea (especially if bloody), stomach cramps, vomiting, or fever. It helps determine whether a bacterial infection is the cause of your symptoms, which is important because treatment differs for bacterial infections versus viral infections or other conditions.

Before the test, follow any instructions your healthcare provider gives you. You may be asked to fast (not eat or drink anything except water) for 8 to 12 hours, avoid certain medications or supplements, and let your provider know about every medicine, vitamin, or herbal product you take so the results can be interpreted correctly.

No special preparation is usually required for this test. However, it is important to inform your doctor about any recent antibiotic use, as this can affect test results. You should also tell your doctor about any recent travel history, as this may affect which bacteria your doctor suspects. Avoid taking antacids, laxatives, or barium supplements before collecting the sample unless directed by your doctor.

The sample is most often collected from a vein in your arm. A trained professional will clean the site, place a tight band around your upper arm, and draw blood into a sterile tube using a small needle. You may feel a brief pinch or sting. For some tests, a urine sample, throat swab, or tissue sample may be needed instead. Afterward, pressure is applied to the site and a small bandage is placed.

You will be given a sterile container for collecting your stool sample. It is important to collect a fresh sample—preferably within 30 minutes of having a bowel movement. The sample should not touch the toilet bowl or toilet water. If possible, collect a sample that contains mucus or blood, as these areas are more likely to contain disease-causing bacteria. For infants, the sample may be collected from a clean diaper.

In the laboratory, trained technologists analyze your sample using specialized equipment and validated methods. They may measure the levels of certain substances, examine cells under a microscope, or run chemical reactions to detect specific markers. The laboratory follows strict quality-control procedures to make sure your results are accurate and reliable before they are released to your healthcare provider.

In the laboratory, the stool sample is placed on special culture plates that allow bacteria to grow. Technicians monitor the cultures to see which bacteria develop. If bacteria grow, they are identified and may be tested for antibiotic susceptibility (sensitivity testing) to help determine which antibiotics will be most effective for treatment.

Your results are usually reported as numbers alongside a reference range, which is the range of values typically seen in healthy people. A result outside this range does not always mean you are ill, since factors such as age, sex, medications, and recent meals can affect the values. Your healthcare provider will review the results with you, explain what they mean in the context of your overall health, and discuss any follow-up testing or treatment that may be needed.

If the test result is 'negative' or 'no pathogens identified,' it means no disease-causing bacteria were found in your stool sample. Your symptoms may be caused by a virus, parasite, or non-infectious cause. If the test result is 'positive,' it means a specific harmful bacterium was identified. Your doctor will discuss the findings with you and recommend appropriate treatment.