Stool (feces) specimen
- Orange top vial/container or sterile tightly capped container (provided by lab) OR container with a preservative (Buffered glycerol saline for Salmonella and Shigella, modified Carey-Blair for C. difficile
- Submit 1-2 g (1-2 mL) of stool
- Rectal swab (if stool collection not possible)
Additional information
- Stool collection:
- Clear instructions should be communicated and given in writing to the patient to ensure proper collection
- Instruct the patient to defecate in a large-mouthed plastic container, bag, or clean bedpan
- If the patient has diarrhea, a large plastic bag is attached by adhesive tape to the toilet seat
- Wear gloves, collect the portions containing pus, blood, or mucus in the stool specimen and transfer it to a container using a clean tongue blade or similar object
- Provide for and respect the person's privacy
- Rectal swab collection:
- The swab is inserted beyond anal sphincter, rotated gently, and withdrawn
- The swab is placed in a clean dry culture container
- Swabbing of lesions of rectal wall or sigmoid colon during proctoscopy or sigmoidoscopy is preferred
- Stool can be collected from the diaper of an infant or incontinent adult
- Samples can be collected from temporary ostomy bags
- Empty bladder completely to avoid contamination with water, urine or other body secretions such as menstrual blood
- Collect specimens before antimicrobial therapy is started
- Do not use laxative, barium sulfate, mineral oil, bismuth, antidiarrheal therapy or antiparasitic therapyat least 2 weeks prior to the test
- Label the samples properly, including date and time of the collection of stool
- Indicate suspected cause of enteritis and current antimicrobial therapy on the lab request
- Send the specimen to lab within 1-2 hrs of passage and do not refrigerate
- 3 separate random stool specimens to be collected every other day, preferably within 10 days, irrespective of previous negative cultures
- Stool culture is performed to isolate and identify pathogenic bacteria or an overgrowth of usual bacterial flora in the intestine
- Culture, when positive for pathogenic bacteria is followed by antibiotic susceptibility testing
- Pathogenic bacteria found in stool may include:
- Salmonella
- Shigella
- Campylobacter
- E. coli (Enteroinvasive, enterohemorrhagic, Enterotoxigenic species)
- Aeromonas
- Plesiomonas
- Staphylococcus
- Vibrio cholerae or parahaemolyticus
- Yersinia
- Cultures for yeast, Bevdomonas, Yersinia, and Vibrio may have to be specifically requested depending on lab practice
- In comparison to other types of cultured specimens, feces contains the greater number and greatest variety of organisms, with more than 50 kinds of bacteria, viruses, fungi, or parasites known to cause disease
- The clinical utility of stool culture and susceptibility testing includes:
- Evaluation, identification, and antibiotic susceptibility testing of pathogenic organisms in patients with gastrointestinal symptoms
- Evaluation in certain conditions or in persons at high risk of intestinal infection, such as:
- Bloody diarrhea
- Fever
- Tenesmus
- Recent travel to a third world country
- Close contact with infected person
- Presence of fecal leukocytes
- Presence of occult blood in feces
- Persons on long term antibiotic therapy (suppressed normal intestinal flora, C. difficile, C. albicans, S. aureus, and P. aeruginosa are common)
- Immunosuppressed persons (AIDS, neoplastic disease, transplantation, cirrhosis, collagen vascular disease, renal failure requiring hemodialysis, and those on immunosuppressive drugs)
- Evaluation of certain intestinal conditions, as a standard work-up, such as:
- Cholera
- Crohn's disease
- Food poisoning
- Irritable bowel syndrome
- Pseudomembranous colitis
- Typhoid
- Ulcerative colitis
- To identify persons who may not have symptoms of any disease but are carriers
- To assist in the differential diagnosis of diarrhea from non-infectious causes such as
- Antibiotics
- Chemotherapeutic drugs
- Crohn's disease
- Endocrine disorders
- Food additives such as sorbitol, fructose
- Food allergies
- Gastrointestinal malignancies
- Heredity disorders
- Medications
- Previous surgery or radiation of the abdomen or gastrointestinal tract
- As an aid to distinguish bacterial from viral (Rotavirus, Adenovirus, Norwalk virus, Astrovirus etc.) gastroenteritis
- Evaluation of therapeutic efficacy in the treatment of gastrointestinal infection
- For epidemiologic purposes especially involving food handlers
- Transmission of gastrointestinal infection is primarily by fecal-oral route through contaminated food and water, undercooked eggs and meat, or unpasteurized milk
- Symptoms of gastrointestinal infection by pathogenic bacteria includes:
- Abdominal pain/cramping
- Anorexia
- Bloating
- Diarrhea
- Fever
- Nausea
- Prostration
- Stools with blood and/or mucous
- Vomiting
- The common causative organisms, which are detectable by stool culture include:
- Salmonella
- Shigella
- Campylobacter jejuni
- Aeromonas
- Plesiomonas
- Staphylococcus aureus
- E. coli O157:H7
- E. coli (Enterohemorrhagic, Enterotoxigenic, Enteroinvasive)
- Clostridium difficile
- Clostridium perfringens
- Yersinia enterocolitica
- Clostridium botulinum
- Vibrio cholerae
- Vibrio parahaemolyticus
- Yeast
- Certain medical conditions that predispose to gastrointestinal infections include:
- Clostridium difficile - Hospitalization, antibiotic administration
- Plesiomonas species – Liver disease or malignancy
- Salmonella species - Intestinal dysmotility, malnutrition, achlorhydria, hemolytic anemia (especially sickle cell disease), immunosuppression, malaria
- Rotavirus – Hospitalization
- Organisms that cause food poisoning include:
- Campylobacter and Salmonella species – from dairy products
- Salmonella species – from egg, raw meat and milk
- Shigella - from salads (especially potato, sea food, meat or pasta) raw vegetables, milk, dairy products, poultry or contaminated water
- C. botulinium – in canned, vaccum packed or modified atmosphere food
- C perfringens, Aeromonas, Campylobacter, and Salmonella species – from meat
- Enterohemorrhagic E coli – Beef
- Campylobacter species – Poultry
- C perfringens, Y enterocolitica – Pork
- Astrovirus, Aeromonas, Plesiomonas, and Vibrio species – Seafood
- Calicivirus, Plesiomonas and Vibrio species – Oysters, shell fish
- Aeromonas species, C perfringens – Vegetables
- Bacillus cereus – from cereal, rice, meat, milk, vegetables, and fish
- Giardia lamblia - from ingestion of water or food contaminated with human sewage
- Listeria monocytogenes – from commercially chilled foods such as prepared salads, sandwiches, paté, cooked meat and ready meals. Also suspected in milk, ice cream, raw and smoked fish, soft cheese
- Common opportunistic organisms causing gastrointestinal infection in immunosuppressed persons, detectable by stool culture, include:
- Staphylococcus aureus
- Salmonella
- Streptococcus
- Shigella
- Campylobacter
- Listeria
- Legionella
Additional information
- Campylobacter jejuni is a leading cause of bacterial gastroenteritis in U.S.
- E.coli strains causing diarrhea include:
- Enterotoxigenic E. coli (ETEC) produce enterotoxins, and is a common cause of travelers diarrhea
- Enteropathogenic E. coli (EPEC) do not produce enterotoxins or invade mucosa, but may cause prolonged diarrhea, especially diarrheal outbreaks in nurseries
- Enteroadherent E. coli (EAEC) causes watery diarrhea, predominantly in travelers
- Enteroinvasive E. coli (EIEC) causes high fever with a toxic appearance and bloody mucous stools
- Enterohemorrhagic E. coli (EHEC) causes bloody diarrhea and low-grade fever, and is associated with hemolytic uremic syndrome (HUS). E. coli O157:H7 is the predominant serotype
- Blood culture may be positive before stool cultures in enteric fever caused by Salmonella typhi, S. choleraesuis, or S. enteritidis
- Rectal swab culture is not as effective as a stool culture for recovery of enteric pathogens or detection of the carrier state
- Factors interfering with test results include:
- Persons having received antibiotics, laxatives, barium sulfate, mineral oil, bismuth, antidiarrheal therapy or antiparasitic therapywithin the 2 weeks preceding the stool specimen collection
- Bismuth found in paper towels and toilet tissue
- Specimen not transported promptly
- Improper collection technique or collection of too few specimens
- Exposure of specimen to excessive heat or cold
- Stool specimen contaminated with urine, water, residual soap, or disinfectants
- Stool collected from toilet bowl may contain other organisms
- Related laboratory tests include
- Complete blood count
- Fecal leukocytes
- Fecal occult blood
- Stool ova and parasites
- Toxin detection assays (Stool for C. difficile toxin)
A normal culture result is:
No growth of pathogenic bacteria
Stool will have growth of normal bacteria; but laboratory testing is focused on pathogenic bacteria. Normal flora may include:
- Clostridium species
- Enterobacteriaceae (various species)
- Enterococcus species
- Escherichia coli (Non-pathogenic strains)
- Proteus species
- Pseudomonas
- Staphylococcus species
- Streptococcus species
- Yeast species (Candida albicans and others)
A positive stool culture for pathogenic bacteria is indicative of infection of the gastrointestinal tract with the isolated bacteria.
A negative stool culture result may be a false negative. Continued collection of stools for testing every 2-3 days for a total of 3 specimens may be indicated if the patient continues to have symptoms or if clinically indicated.
- Amar CF et al. Blinded application of microscopy, bacteriological culture, immunoassays and PCR to detect gastrointestinal pathogens from faecal samples of patients with community-acquired diarrhoea. Eur J Clin Microbiol Infect Dis. 2004 Jul;23(7):529-34. Epub 2004 Jun 16.
- ARUP Laboratories®. Stool Culture, Routine (Includes E. coli Shiga-like Toxin by EIA 0060047). [Homepage on the internet]©2007. Last accessed on March 5, 2007. Available at URL: http://www.aruplab.com/guides/ug/tests/0060134.jsp
- Centers for Disease Control: Collection and Preservation of Fecal Laboratory Specimens. [Homepage on the Internet]. Last accessed on March 5, 2007. Available at URL: http://www.dpd.cdc.gov/DPDx/CEUs/Lab_tech_ceu.asp?body=Lab_Tech/body_labtech_directions.htm
- Centers for Disease Control: Chronic Diarrhea. [Homepage on the Internet]. Last accessed on March 5, 2007. Available at URL: http://www.cdc.gov/ncidod/dpd/parasites/diarrhea/factsht_chronic_diarrhea.htm
- eMedicine from WebMD®. Diarrhea. [Homepage on the Internet] ©1996-2006. Last updated on October 4, 2006. Last accessed on March 5, 2007. Available at URL: http://www.emedicine.com/ped/topic583.htm
- Hatta M et al. Detection of Salmonella typhi by nested polymerase chain reaction in blood, urine, and stool samples. Am J Trop Med Hyg. 2007 Jan;76(1):139-43.
- Klein EJ et al. Diarrhea etiology in a Children's Hospital Emergency Department: a prospective cohort study. Clin Infect Dis. 2006 Oct 1;43(7):807-13. Epub 2006 Aug 22.
- Laboratory Corporation of America. Stool Culture. [Homepage on the internet]©2007. Last accessed on March 5, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/mb012800.htm
- LabTestsOnline®. Stool Culture. [Homepage on the Internet]© 2001-2006. Last reviewed onDecember 26, 2004. Last accessed on March 5, 2007. Available at URL: http://www.labtestsonline.org/understanding/analytes/stool_culture/glance.html
- Mathieu A et al. [When should a stool culture be done in adults with nosocomial diarrhea?] [Article in French]. Presse Med. 2005 Jan 29;34(2 Pt 1):81-4.
- Pradel N et al. Prevalence and characterization of Shiga toxin-producing Escherichia coli isolated from cattle, food, and children during a one-year prospective study in France. J Clin Microbiol. 2000 Mar;38(3):1023-31.