Stool Culture

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Also known as: Bacterial Culture, stool; Feces Culture
Formal name: Enteric Pathogens Culture, stool

At a Glance

Why Get Tested?

To determine whether you have an infection of your digestive tract due to the presence of disease-causing (pathogenic) bacteria

When to Get Tested?

When you have diarrhea, abdominal cramps, with or without fever, lasting more than a few days

Sample Required?

A fresh stool sample or one that has been placed in a transport medium (a collection vial containing a preservative)

Test Preparation Needed?

None

The Test Sample

What is being tested?

The stool culture is a test that detects and identifies bacteria that cause infections of the lower digestive tract. The test distinguishes between the types of bacteria that cause disease (pathogenic) and the types that are normally found in the digestive tract (normal flora). The test helps to determine if pathogenic bacteria are the cause of gastrointestinal symptoms (gastroenteritis).

The bacteria found in stool are representative of the bacteria that are present in the gastrointestinal tract. Certain bacteria and fungi called normal flora inhabit everyone's gastrointestinal tract. They play an important role in the digestion of food, and their presence keeps a check on the growth of disease-causing bacteria. Sometimes, the balance of the normal flora may be affected by the administration of broad-spectrum antibiotics; the drugs inhibit the growth of normal flora and allow bacteria resistant to the antibiotic to survive and overgrow the digestive tract. The normal flora may also be affected by anti-cancer drugs and when a person has a weakened immune system, leading to bacterial overgrowth and symptoms such as diarrhea and abdominal pain. 

Pathogenic bacteria can enter and infect the digestive tract when someone eats food or drinks water that is contaminated. Examples of contaminated sources include raw or undercooked eggs, poultry or beef, unpasteurized milk, and untreated water from lakes, streams, and (occasionally) from community water supplies.

People who travel outside the U.S., especially to developing nations, may face a greater risk of being exposed to disease-causing bacteria. Some of these bacteria may be true pathogens while others are strains of gastrointestinal bacteria that are normal flora for the local inhabitants but cause gastrointestinal distress to the tourist. Visitors may become infected by eating or drinking anything that has been contaminated with the bacteria, even things as simple as tap water, ice cubes in a drink, a fresh salad, or food from a vendor's stall.

The most common symptoms of a pathogenic bacterial infection are prolonged diarrhea, bloody diarrhea, mucus in the stool, abdominal pain and cramping, and nausea. If diarrhea lasts more than a few days, it may lead to complications such as dehydration and electrolyte imbalance - dangerous conditions, especially in children and the elderly. Dehydration can cause symptoms such as dry skin, fatigue, and light-headedness.

Severely affected people may require hospitalization to replace lost fluids and electrolytes. Hemolytic uremic syndrome is a serious complication characterized by the destruction of red blood cells and kidney failure that may occasionally arise from an infection with a toxin-producing strain of the bacteria Escherichia coli. The condition is most frequently seen in children, the elderly, and those with weakened immune systems.

Some of the most common pathogenic bacteria that cause infections in the U.S. and their most frequently encountered sources include:

  • Salmonella - found in raw eggs (even intact disinfected eggs), raw poultry uncooked vegetables, and in reptiles; pets, such as lizards and turtles, may carry salmonella in their intestines without being ill themselves. Some humans may become carriers of salmonella. Salmonella may be transmitted person-to-person.
  • Shigella - found in food and water contaminated with stool, and from infected-person to person when careful sanitation is not observed; for instance, it can be a challenge to prevent the spread of Shigella within a family and in a daycare or nursing home setting since even a very few organisms may cause disease.
  • Campylobacter - found in raw or undercooked poultry; it is the most common cause of bacterial diarrhea in the U.S. It may become especially serious if it spreads to the bloodstream, and it occasionally causes long-term complications such as arthritis and Guillain-Barré syndrome.
  • Escherichia coli 0157:H7 and other toxin-producing E. coli (most strains of E. coli are considered normal flora and do not cause disease) - found in raw or undercooked hamburger/beef, spinach, or unpasteurized cider; causes bloody diarrhea and may lead to hemolytic uremic syndrome.
  • Clostridium difficile - may be present as part of the normal flora, but use of broad-spectrum antibiotics can result in an overgrowth of these bacteria. Toxin-producing strains can cause diarrhea and other serious complications.

A wide variety of other bacteria may sometimes cause diarrhea. These may include: Aeromonas species, Staphylococcus aureusYersinia enterocolitica, Vibrio cholerae and other Vibrio species.

How is the sample collected for testing?

A fresh stool sample is collected in a sterile container. The stool sample should not be contaminated with urine or water. Once it has been collected, the stool should be taken to the laboratory within about an hour after collection or should be transferred into a vial containing a preservative and taken to the lab as soon as possible. For infants, a stool sample is usually collected with a swab of the rectum. 

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

(2011 January). Diarrhea. National Digestive Diseases Information Clearinghouse [On-line information]. Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/diarrhea/ through http://digestive.niddk.nih.gov. Accessed May 2011.

Guandalini, S. (Updated 2010 April 8). Diarrhea. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/928598-overview through http://emedicine.medscape.com. Accessed May 2011.

Vorvick, L. et. al. (Updated 2010 May 4). Fecal culture. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003758.htm. Accessed May 2011.

Fisher, M. (Updated 2011 April). Diarrhea, Bacterial Evaluation. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/BacterialDiarrhea.html?client_ID=LTD through http://www.arupconsult.com. Accessed May 2011.

(© 1995–2011). Unit Code 50005: Enteric Pathogens Culture, Stool. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/50005 through http://www.mayomedicallaboratories.com. Accessed May 2011.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 911-912.

Forbes BA, Sahm DF, Weissfeld AS. Bailey & Scott’s Diagnostic Microbiology 12th Edition: Mosby Elsevier, St. Louis, MO; 2007, Pp 873-883.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

(2003 March 6). Diarrheagenic Escherichia coli. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/diarrecoli_t.htm through http://www.cdc.gov.

(2002 September 6). Campylobacter Infections. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/campylobacter_g.htm through http://www.cdc.gov.

(2003, July 3, Updated). Escherichia coli O157:H7. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm through http://www.cdc.gov.

(2001 March 08). Escherichia coli O157:H7, Technical Information. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_t.htm through http://www.cdc.gov.

(2003 March 7). Salmonella Enteritidis. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/salment_g.htm through http://www.cdc.gov.

(2003 June 9). Salmonellosis. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/salmonellosis_g.htm through http://www.cdc.gov.

(2003 March 7). Shigellosis. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/shigellosis_g.htm through http://www.cdc.gov.

(2001 June 20). Typhoid Fever. CDC, Division of Bacterial and Mycotic Diseases, Disease Information [On-line information]. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/typhoidfever_g.htm through http://www.cdc.gov.

(2000 April). E. Coli Infection. AAFP, familydoctor.org, Handout [On-line information]. Available online at http://familydoctor.org/handouts/242.html through http://familydoctor.org.

Graha, P. (2002 December 22). Campylobacter Enteritis. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000224.htm.

Kott, C. (2002 February 20). E. coli enteritis. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000296.htm.

Kotton, C. (2002 January 8). Fecal culture. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003758.htm.

Kotton, C. (2001 August 3). Salmonella Enterocolitis. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000294.htm.

Parsons, C. (2002 July 31). Shigella enteritis. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000295.htm.

Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 887.

Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 1607-1610.

Lentnek, A. (2007 November 12, Updated). Fecal Culture. MedlinePlus Medical Encyclopedia [On-line information]. Accessed on: 1/30/08. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003758.htm.