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Clostridium difficile and C. difficile Toxin Testing

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Also known as: C. difficile; C. diff
Formal name: Clostridium difficile Culture; C. difficile Toxin, A and B; C. difficile Cytotoxin Assay; Glutamate Dehydrogenase Test
Related tests: Stool Culture; O&P

At a Glance

Why Get Tested?

To detect the presence of an infection caused by toxin-producing Clostridium difficile bacteria

When to Get Tested?

When a person has mild, moderate, or severe diarrhea that persists for several days with abdominal pain, loss of appetite, and fever, following antibiotic therapy

Sample Required?

A fresh or refrigerated liquid or unformed stool sample that has not been contaminated with urine or water

Test Preparation Needed?


The Test Sample

What is being tested?

These tests detect an infection of the digestive tract by toxin-producing Clostridium difficile. These are bacteria that may be present as part of the normal bacterial flora in the digestive tract; they are present in up to 65% of healthy infants and 3% of healthy adults. Sometimes, when broad-spectrum antibiotics are used to treat infections, the balance of the normal flora in the digestive tract is disrupted. Normal bacterial flora that are susceptible to the antibiotic are eliminated from the digestive tract, while C. difficile that are resistant to the antibiotic remain and begin to overgrow, or new types (strains) of C. difficile are acquired.

The strain of C. difficile that is present may produce two toxins: toxin A and toxin B. The resulting combination of decreased normal flora, overgrowth of C. difficile, and toxin production can damage the lining of the lower portion of the digestive tract (colon) and lead to severe inflammation of the colon and prolonged diarrhea. Dead tissue, fibrin, and numerous white blood cells can form a lining over the surface of the inflamed bowel (a pseudomembrane), a condition that is referred to as pseudomembranous colitis.

Production of toxin by C. difficile is the most common cause of diarrhea in people who develop diarrheal symptoms while hospitalized. C. difficile toxin is detected in the stools of up to 20-30% of those with antibiotic-associated diarrhea and greater than 95% of those with pseudomembranous colitis. While the organism is frequently carried by infants, it does not usually cause diarrhea in this population. The risk of being symptomatic increases with age and increases in those who have weakened immune systems, have acute or chronic colon conditions, have been previously affected by C. difficile, or who have had recent gastrointestinal surgery or chemotherapy. C. difficile-associated diarrhea usually occurs in people who have been taking antibiotics for several days, but it can also occur several weeks after treatment is completed.

C. difficile-associated disease is a spectrum of illness ranging from mild diarrhea to a more severe colitis, or to toxic megacolon or perforated bowel, which can result in sepsis and death. Signs and symptoms may include frequent loose stools, abdominal pain and cramps, nausea, fever, dehydration, fatigue, and high white blood cell count (leukocytosis). Treatment typically involves discontinuing use of the original antibiotic and administering specific oral antibiotic therapy to which the C. difficile is susceptible. Most people improve as the normal flora re-establish, but about 12-24% of those affected may have a second episode within 2 months.

How is the sample collected for testing?

A fresh liquid or unformed 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 immediately or refrigerated and taken to the lab as soon as possible.

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

Vorvick, L (Updated 2010 April 12). Stool C. difficile toxin. MedlinePlus Medical Encyclopedia [On-line information]. Available online at Accessed May 2011.

(Updated 2011 January 25). Information about the Current Strain of Clostridium difficile. Centers for Disease Control and Prevention [On-line information]. Available online at through Accessed May 2011.

(Reviewed 2010 November 25). Frequently Asked Questions about Clostridium difficile for Healthcare Providers. Centers for Disease Control and Prevention [On-line information]. Available online at through Accessed May 2011.

Mayo Clinic Staff (2010 November 3). C. difficile. [On-line information]. Available online at through Accessed May 2011.

Fisher, M and She, R. (Updated 2010 November). Clostridium difficile. ARUP Consult [On-line information]. Available online at through 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 270-271.

Stuart H. Cohen et al. Clinical Practice Guidelines for Clostridium difficile Infection in Adults: 2010 Update by the Society for Healthcare Epidemiology of America (SHEA) and the Infectious Diseases Society of America (IDSA). Infection Control and Hospital Epidemiology. Available online at through Published online March 22, 2010. Accessed April 20, 2010.

Forbes, B. et. al. (© 2007). Bailey & Scott's Diagnostic Microbiology, 12th Edition: Mosby Elsevier Press, St. Louis, MO. Pp 463, 889.

(March 8, 2011) Aberra F, et al. Clostridium difficile Colitis. eMedicine article. Available online at through Accessed May 2011.

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.

Hamm, L (2000 June 01) Clostridium difficile. Medscape Today [On-line article from Pediatric Pharmacotherapy]. Available online at through

Yousuf, K., et. al.(2002 August 16). Clostridium Difficile-Associated Diarrhea and Chronic Renal Insufficiency. Medscape Today [On-line article from South Med J 95(7):681-683, 2002]. Available online at through

Kovacs, D., et. al. (2000). Recurrent Clostridium difficile-Associated Diarrhea and Colitis Treated With Saccharomyces cerevisiae (Baker's Yeast) in Combination With Antibiotic Therapy: A Case Report. Medscape Today [On-line article from J Am Board Fam Pract 13(2):138-140, 2000]. Available online at through

Carroll, D. (2004 February 23). Moxifloxacin-Induced Clostridium difficile-Associated Diarrhea. Medscape Today [On-line article from Pharmacotherapy 23(11):1517-1519, 2003]. Available online at through

Connor, B. and Landzberg, B. (2003 June 17). Travel Medicine, Persistent Traveler's Diarrhea. Medscape Today [Online article from Infect Med 20(5):242-244, 247, 2003]. Available online at through

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Roth, A. and Basello, G. (2003 December 1). Approach to the Adult Patient with Fever of Unknown Origin. American Family Physician [On-line journal]. Available online at through

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McCusker, M., et. al. (2004 January 5). Fluoroquinolone Use and Clostridium difficile–associated Diarrhea. CDC, Emerging Infectious Diseases [On-line article]. Available online at through

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Forbes BA, Sahm DF, Weissfeld AS, eds., Bailey and Scott's Diagnostic Microbiology, 12th edition, St. Louis, MO (2007).

Henry’s Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007.

Lehrer JK (2007 August 7 Updated). Stool C. difficile toxin. Medlineplus Health Information, Medical Encyclopedia (On-line information, accessed November 2007). Available online at

(June 5, 2007) Centers for Disease Control and Prevention. Clostridium difficile Infections: Overview (online information, accessed November 2007). Available online at through

Sunenshine R, McDonald LC. Clostridium difficile-associated disease: New challenges from an established pathogen. Cleveland Clinic Journal of Medicine (2006) 73:187-197. (Accessed online November 2007). PDF available for download at through

Grossman K. Health information: Toxic megacolon (online information, accessed December 2007). Available online at through

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