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Clostridium difficile
Member of genus Clostridium
Morphology
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.
Cultural characteristics
Clostridium shows optimum 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.
History
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.
Pathogenesis
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.
Diseases caused by C. difficile
Treatment
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.
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