Clostridium difficile

Clostridium difficile

Clostridium difficile

Scientific classification

Kingdom:	Bacteria
Phylum:	Firmicutes
Class:	Clostridia
Order:	Clostridiales
Family:	Clostridiaceae
Genus:	*Clostridium*
Species:	*difficile*

Binomial name

Clostridium difficile

Members of genus Clostridium are gram-positive, anaerobic spore-forming rods. These motile bacteria are ubiquitous in nature and are especially prevalent in soil. Under the microscope, they appear as long drumsticks with a bulge located at their terminal ends. C. difficile cells are gram positive, while spores are gram negative. Clostridium shows optimimum growth when plated on blood agar at human body temperatures. When the environment becomes stressed, however, the bacteria produce spores that tolerate the extreme conditions that the active bacteria cannot. First described by Hall and O'Toole in 1935, "the difficult clostridium" was resistant to early attempts at isolation and grew very slowly in culture.

With the introduction of broad-spectrum antibiotics in the latter half of the twentieth century, antibiotic-associated diarrhea became more common. Pseudomembranous colitis was first described as a complication of C. difficile infection in 1978, when a toxin was isolated from patients suffering from pseudomembranous colitis.

C. difficile is an infrequent inhabitant of the human intestine. Antibiotics, especially those with a broad spectrum of activity, cause disruption on normal intestinal flora. C. difficile is resistant to most antibiotics. It flourishes under these conditions. It is transmitted from person to person by the fecal-oral route. Because the organism forms heat-resistant spores, it can remain in the hospital or nursing home environment for long periods of time. It can be cultured from almost any surface in the hospital. Once spores are ingested, they pass through the stomach unscathed because of their acid-resistance. They change to their active form in the colon and multiply.

Pathogenic strains will elaborate one of two toxins, toxin A or B. These toxins are responsible for the diarrhea and inflammation seen in patients so infected. Infection can range in severity from asymptomatic to severe and life threatening. People are most often infected in hospitals, nursing homes or institutions, although C. difficile infection in the community, outpatient setting is increasing.

Two antibiotics are effective against C. difficile. Metronidazole is first choice because of superior tolerability, lower price and comparable efficacy. Oral vancomycin can be used as well.

On June 4, 2004, two outbreaks of a highly virulent strain of this bacterium were reported in Montreal, Quebec and Calgary, Alberta, in Canada. Sources put the death count as low as 36 and as high as 89, with approximately 1,400 cases in 2003 and within the first few months of 2004.