Stool culture

Stool culture is a test to identify bacteria in patients with a suspected infection of the digestive tract. A sample of the patient's feces is placed in aspecial medium where bacteria is then grown. The bacteria that grow in the culture are identified using a microscope and biochemical tests.

Stool culture is used to identify bacteria or other germs in people with symptoms of stomach or intestinal infection, most often diarrhea. Identificationof the organism is necessary to determine how to treat the patient's infection.

Stool culture is only performed if an infection of the digestive tract is suspected. The test has no harmful effects.

Stool culture also may be called fecal culture. To obtain a specimen for culture, the patient is asked to collect a stool sample into a special sterile container that may contain a solution. Specimens may need to be collected on three consecutive days. It is important to return the specimen to the doctor'soffice or the laboratory in the time specified by the doctor or nurse. Labs don't accept stool specimens contaminated with water, urine, or other materials.

The culture test involves placing a sample of the stool on a special substance called a medium that provides nutrients for certain organisms to grow and reproduce. The medium is usually a thick gel-like substance. The culture is done in a test tube (or on a flat round culture plate) which is kept at the proper temperature so bacteria can grow. After bacteria begin to grow in the medium, they are identified by observing physical characteristics and microscopic features. The bacteria may be dyed with special stains that make it easierto identify their features.

The length of time needed to perform a stool culture depends on the lab whereit is done and the culture methods used. Stool culture usually takes 72 hours or longer to complete, but some organisms may take several weeks to grow ina culture.

An antibiotic sensitivity test may be done after a bacteria is identified toshow which antibiotics will work the best in treating the infection.

Although most intestinal infections are caused by bacteria, in some cases a fungal or viral culture may be necessary.

Several intestinal parasites may cause gastrointestinal infection and diarrhea. Parasites are not cultured, but are identified microscopically in a test called "Stool Ova and Parasites."

Insurance coverage for stool culture may vary among different insurance plans. This common test usually is covered if ordered by an insurance-approved doctor at an approved lab.

The doctor or other healthcare provider will ask the patient for a complete medical history and perform a physical examination to determine possible causes of the problem. Information about the patient's diet, medications and recent travel may provide clues to the identity of possible infectious organisms.

Stool culture normally doesn't require any special preparation. Patients don't need to change their diet before collecting the specimen, but they should avoid castor oil, bismuth, and laxative preparations containing psyllium hydrophilic mucilloid that might contaminate the specimen.

Infection-causing bacteria that aren't normally found in the digestive tractinclude Shigella, Salmonella, Campylobacter, and Yersinia. Clostridium difficile produces a toxin that can cause severe diarrhea. Other bacteria that produce toxins are Staphylococcus aureus, Bacillus cereus, and Escherichia coli. Although Escherichia coli is a normal bacteria found in the intestines, one toxic type ofthis bacteria can be acquired from eating contaminated meat, juice, or fruits. It produces a toxin that causes severe inflammation and bleeding of the colon.

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