stool culture


Also found in: Dictionary, Thesaurus.
Related to stool culture: Blood culture, Urine Culture

Stool Culture

 

Definition

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 a special medium where bacteria is then grown. The bacteria that grow in the culture are identified using a microscope and biochemical tests.

Purpose

Stool culture is performed to identify bacteria or other organisms in persons with symptoms of gastrointestinal infection, most commonly diarrhea. Identification of the organism is necessary to determine the treatment of the patient's infection or to trace the cause of an outbreak or epidemic of certain types of diarrhea.
According to the Centers for Disease Control and Prevention (CDC), doctors are most likely to order a stool culture for patients with any of the following characteristics: AIDS, bloody stools, diarrhea lasting longer than three days, high fever, history of recent travel abroad, or severe dehydration.

Precautions

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

Description

Stool culture may also be called fecal culture. To obtain a specimen for culture, the patient is asked to collect a stool sample into a special sterile container. In some cases, the container may contain a transport solution. Specimens may need to be collected on three consecutive days. It is important to return the specimen to the doctor's office or the laboratory in the time specified by the physician or nurse. Laboratories do not 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 incubated at the proper temperature for growth of the bacteria. After a colony of bacteria grows in the medium, the type of bacteria is identified by observing the colony's growth, its physical characteristics, and its microscopic features. The bacteria may be dyed with special stains that make it easier to identify features specific to particular bacteria.
The length of time needed to perform a stool culture depends on the laboratory where it is done and the culture methods used. Stool culture usually takes 72 hours or longer to complete. Some organisms may take several weeks to grow in a culture.
An antibiotic sensitivity test may be done after a specific bacterium is identified. This test shows which antibiotics will be most effective for treating the infection.
Although most intestinal infections are caused by bacteria, in some cases a fungal or viral culture may be necessary. The most common bacterial infections of the digestive tract are caused by Shigella, Salmonella, Campylobacter, and Yersinia. Patients taking certain antibiotics may be susceptible to infection with Clostridium difficile. In some cases, as with Clostridium difficile, the stool culture is used to detect the toxin (poison or harmful chemical) produced by the bacteria.
Patients with AIDS, or other immune system diseases, may also have gastrointestinal infections caused by such fungi as Candida, or viral organisms including cytomegalovirus.
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 a physician approved by the patient's insurance plan, and if it is done at an approved laboratory.

Alternative methods

Newer methods of testing stool samples for specific disease organisms include various forms of polymerase chain reaction (PCR) assays. One type that has been used to test for several different types of intestinal viruses at the same time is the RT-PCR, which stands for reverse transcriptase polymerase chain reaction. This assay measures changes in an organism's messenger RNA. RT-PCR assays have several advantages over standard stool cultures: they require only very small samples of material; they can be performed much more rapidly; and they can be used to test environmental water for virus contamination as well as human stool samples.

Preparation

The physician or other healthcare provider will ask the patient for a complete medical history and perform a physical examination to determine possible causes of the gastrointestinal problem. Information about the patient's diet, any medications taken, and recent travel may provide clues to the identity of possible infectious organisms.
Stool culture normally doesn't require any special preparation. Patients do not need to change their diet before collecting the specimen. Intake of some substances can contaminate the stool specimen and should not be taken the day before collection. These substances include castor oil, bismuth, and laxative preparations containing psyllium hydrophilic mucilloid.

Normal results

Bacteria that are normally found in the intestines include Pseudomonas and Escherichia coli. These enteric bacteria (bacteria of the gastrointestinal system) are considered normal flora and usually do not cause infection in the digestive tract.

Abnormal results

Bacteria that do not normally inhabit the digestive tract, and that are known to cause gastrointestinal infection include 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 enterotoxigenic (producing disease in the digestive system) Escherichia coli. Although Escherichia coli is a normal bacteria found in the intestines, the enterotoxigenic type of this bacteria can be acquired from eating contaminated meat, juice, or fruits. It produces a toxin that causes severe inflammation and bleeding of the colon.

Resources

Books

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Disturbances in Newborns and Infants." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Periodicals

Grimm, A. C., J. L. Cashdollar, F. P. Williams, and G. S. Fout. "Development of an Astrovirus RT-PCR Detection Assay for Use with Conventional, RealTime, and Integrated Cell Culture/RT-PCR." Canadian Journal of Microbiology 50 (April 2004): 269-278.
Hennessy, T. W., R. Marcus, V. Deneen, et al. "Survey of Physician Diagnostic Practices for Patients with Acute Diarrhea: Clinical and Public Health Implications." Clinical Infectious Diseases 38, Supplement 3 (April 15, 2004): s203-S211.
Heryford, A. G., and S. A. Seys. "Outbreak of Occupational Campylobacteriosis Associated with a Pheasant Farm." Journal of Agricultural Safety and Health 10 (May 2004): 127-132.
Rohayem, J., S. Berger, T. Juretzek, et al. "A Simple and Rapid Single-Step Multiplex RT-PCR to Detect Norovirus, Astrovirus and Adenovirus in Clinical Stool Samples." Journal of Virological Methods 118 (June 1, 2004): 49-59.
Sloan, L. M., J. R. Uhl, E. A. Vetter, et al. "Comparison of the Roche LightCycler vanA/vanB Detection Assay and Culture for Detection of Vancomycin-Resistant Enterococci from Perianal Swabs." Journal of Clinical Microbiology 42 (June 2004): 2636-2643.

Organizations

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.

Key terms

Bismuth — A substance used in medicines to treat diarrhea, nausea, and indigestion.
Enteric — Pertaining to the intestine.
Enterotoxigenic — Refers to an organism that produces toxins in the gastrointestinal tract that cause such things as vomiting, diarrhea, and other symptoms of food poisoning.
Feces — Material excreted by the intestines.
Flora — Refers to normal bacteria found in a healthy person.
Gastrointestinal — Referring to the digestive tract; the stomach and intestines.
Psyllium hydrophilic mucilloid — A plant material contained in some laxatives.
Sterile — Free of microorganisms.
Toxin — A poison; usually refers to protein poisons produced by bacteria, animals, and some plants.

stool culture

a test to determine whether a patient has a bacterial or viral infection of the bowel or parasites.

stool culture

The placing of a sample of stool in an appropriate culture medium to detect growth of a pathogen–eg, rotavirus, for which specimen is frozen ASAP, or Yersinia enterocolitica–specimen stays at room temperature. See Ova and parasites.
References in periodicals archive ?
In North America, few cases of MRSA colitis have been identified; however, this cause of enteritis might be underreported because few physicians order stool cultures for hospitalized patients with AAC (1,4).
A stool culture should be performed for all children with acute bloody diarrhea.
Hence, making available and promoting comprehensive stool culture tests could directly impact the acute severe watery diarrhea outcomes by identifying causative agents, avoiding antibiotics misuse, reducing hospital stay, complications and patients' inconveniences6,7,9.
However, 17 staff members said they suffered gastroenteritis, seven were positive for salmonella group D and another seven were reported to have salmonella group D isolated in their stool cultures.
3; normal thyroid function tests; normal complete metabolic panel; stool for leukocytes and stool cultures for ova, parasites, Clostridium difficile, Salmonella, Shigella, Campylobacter, Yersinia were negative.
A further stool culture during admission showed no growth of organisms.
Frequency of Shigella species isolated from stool cultures of patients at Children Medical Center Hospital, Tehran, Iran Shigella species Frequency Percent S.
A stool culture is necessary to confirm the diagnosis (Harris, Dupont, & Hornick, 1972).
However, bicarbonate may help rule out dehydration (SOR: B); electrolytes and blood urea nitrogen may be useful in evaluating complicated diarrhea with severe dehydration or when intravenous fluids are required; stool cultures are indicated for bloody or prolonged diarrhea, suspected food poisoning, or recent travel abroad (SOR: C).
I took a stool culture and put him on antibiotics right away," ways Washington internist David Jacobs.
A stool culture ordered by her doctor confirmed she was infected with Shigella sonnei.
Stool culture showed motile gram negative, non- lactose fermenting bacilli with biochemical reaction suggestive of Salmonella typhimurium.