Pathology of Clostridium difficile


Micrograph of Clostridium difficile from a stool sample (From: Public Doman- CDC)How does Clostridium difficile enter the body?

C. difficile enters a person’s body via ingestion of the spores (for more information on spore formation, go to General Characteristics). These spores can survive up to two years on inanimate objects and are spread via the fecal-oral route. The fecal-oral route most often involves someone touching a surface contaminated C. difficile spores and then touching their
mouth with the contaminated hand. (Not surprisingly, HANDWASHING is the best way to prevent C. difficile infections.) After ingestion, spores travel unharmed through the acidic environment of the stomach and germinate into theClipArt of a hand touching a mouth--demonstrating fecal-oral transmission (From: Microsoft ClipArt) vegetative form.


From: (Public Domain) Centers for Disease Control and Prevention. 2009.

       <URL:>. Accessed 31 March 2009

Why does Clostridium difficile cause disease in some people and not in others?

In an otherwise healthy person, the person’s normal microflora of the intestines prevents C. difficile from growing due to limited space and resources. However, when people are taking significant amounts of antibiotics to treat another illness, the antibiotics kill off the normal microflora of the intestines allowing C. difficile to colonize the intestine and grow out of control. C. difficile is most often acquired nosocomially (acquired secondary to a primary hospitalization) because, in the hospital, patients are often on broad-spectrum antibiotic therapy (antibiotics, such as clindamycin, used to treat a number of bacterial infections) to prevent any infection. Nevertheless, these antibiotics can cause pathogenic strains of C. difficile to grow out of control. Pathogenic strains of C. difficile can cause C. difficile- associated disease or CDAD. CDAD affects more than 300,000 hospitalized patients yearly in the United States.

How does Clostridium difficile cause disease?

If the normal microflora of a person infected with C. difficile has Intestine with Pseudomembranous colitis (From: Johnson, M. T. 2009)

been disrupted by antibiotic therapy, C. difficile bacteria are able to reproduce in the intestinal crypts. Pathogenic strains of C. difficile causes disease by the release of two protein enterotoxins, toxin A and toxin B, which cause severe inflammation and mucosal injury to the colon--colitis. At this point, the toxins attract white blood cells to the area, and the white blood cells may provide a protective immune response. However, if the white blood cells do not provide the desired immune response, mild CDAD occurs. Nevertheless, the toxins can actually kill the lining of the intestine, causing it to fall off and mix with the white blood cells and give the appearance of yellow plaques (patches) in the intestines. This is called pseudomembranous colitis because the patches look like membranes but aren’t true membranes.  (Check out this video of a colonoscopy of a colon with pseudomembranous colitis and note the yellow
patches in the intestines.)

                                                                 From: Johnson, M. T. 2009. Medical Microbiology
                               Accessed 7 April 2009.

What are the symptoms of mild CDAD and severe pseudomembranous colitis?


* Non-bloody, watery diarrhea (5-10 watery stools a day)

* Low-grade fever

*Abdominal cramping



*Loss of appetite

Pseudomembranous colitis (in addition to mild symptoms)

*Profuse watery diarrhea (greater than 10 watery stools a day)

*High fever (102°F—104°F)

*Blood in the stool

*Weight loss

*Severe abdominal pain and tenderness

*Death (6%-30% mortality rate)


For information on treatments for CDAD and pseudomembranous colitis, check out the treatment page.

Who is most likely to get a Clostridium difficile infection?

People who:

*are taking more than one kind of antibiotic

* have prolonged hospitalizations

*are elderly

*already have a disease of the intestines

*are undergoing chemotherapy

*have other serious diseases

Pathogenesis of Clostridium difficile-Associated Disease


Pathogenesis of CDAD (Created using Microsoft PowerPoint, Adapted from ED/LS 2007-Southend University Hospital)


Adapted from: ED/LS. 2007. Southend University Hospital
                          Accessed 7 April 2007.

Now that you have learned how C. difficile causes disease, you should learn how the disease is diagnosed, treated, and prevented.