Clostridium difficile, first identified in 1935, is a gram-positive bacterium linked to antibiotic-associated diarrhea and colitis due to its production of two toxins that disrupt intestinal function. It can affect healthy individuals and is often acquired in healthcare settings, exacerbated by antibiotic use, which alters gut flora. Diagnosis relies on detecting toxins in stool samples, with treatment usually involving antibiotics like metronidazole or vancomycin for symptomatic patients.

1. CLOSTRIDIUM DIFFICILE

2. Background history.
C. difficile was first described in 1935 from the feces of healthy
newborns and was initially not thought to be a pathogen.
It was named difficile because it grows slowly and is difficult to culture
. It is a long slender Gram-positive, anaerobic bacillus
bearing large, oval, and terminal spores.
It is nonhemolytic, saccharolytic, and mild proteolytic.

3.  C. difficile is the causative agent of antibiotic-associated diarrhea and colitis.
 C. difficile produces two antigenically distinct toxins: toxin A and toxin B.
Toxin A is an enterotoxin and toxin B is a cytotoxin. Both the toxins contribute
pathogenesis of C. difficile colitis and diarrhea in humans.
 Both are proteins which bind to specific receptors present in the mucosa of
intestine.
 The toxins gain entry into cells and catalyze a specific alteration of Rho prote
and glutamyl
transpeptidase (GTP)-binding proteins that help in actin polymerization,
cytoskeletal architecture,
and cell movement.

4. Epidemiology
C. difficile is part of the normal intestinal flora in a small number of healthy people and
hospitalized patients.
In contrast with the original belief that C. difficile disease is restricted to hospitalized patients,
it is now recognized that a significant proportion of individuals with C. difficile disease develops
symptomatic disease outside the hospital.
For most of these patients, they have a recent history of exposure to a health care facility, where
they were presumably exposed to C. difficile, and antibiotic use. The disease develops in people
taking antibiotics, because the drugs alter the normal enteric f lora, either permitting overgrowth of
these relatively resistant organisms or making the patient more susceptible to exogenous
acquisition of C. difficile.
The disease occurs if the organisms proliferate in the colon and produce their toxins

5. Pathogenesis
•Resistance to certain antibiotics may permit overgrowth
or acquisition of C. difficile in patients receiving these drugs for other
infections.
•Enterotoxin (toxinA) promotes fluid secretion and
intestinal hemorrhage (similar to choleratoxin).
•Cytotoxin (toxinB) damages mucosal membranes by depolymerizing
cellular cytoskeleton.
•Adhesion factor binds to human colon cells.
•Spores are insensitive to oxygen and resistant to many
disinfectants,
including alcohol based hand cleaners, making their elimination from
hospital environments difficult.

6. Laboratory Diagnosis
Isolation of the C. difficile in stool culture documents colonization
but not disease, so the diagnosis of disease is confirmed by
demonstration of the enterotoxin or cytotoxin in a stool specimen
from a patient with compatible clinical symptoms or detection of
the C. difficile toxin genes directly in clinical specimens by nucleic
acid amplification techniques.
Commercial assays with high sensitivity and specificity are now
available that provide results within a few hours of sample
collection.

7. Diagnosis
Diagnosis of C. difficile diarrhea is made by demonstration of C. difficile toxin in the feces by stool
cytotoxin test and by enzyme-linked immunosorbent assay:
■ The stool cytotoxin test is the test of choice. In this test,
diarrheal stool is filtered and then inoculated to Hep-2 and
human diploid cell cultures.
 The demonstration of a cytopathic
effect that is neutralized by specific antiserum indicates
the presence of the toxin (positive test).
 Absence of
cytopathic effect is considered a negative test. The test has
a high sensitivity of 94–100% and a specificity of 99%.
NOTE:
Disadvantage
of the test are that it is expensive and it requires a
tissue culture facility.

8. ■ Several enzyme immunoassays with moderate sensitivity
(69–87%) and high specificity (99–100%) are now commercially
available for rapid detection of the toxin and diagnosis.
The latex agglutination test has been employed to detect
the presence of glutamate dehydrogenase, produced by
C. difficile, for diagnosis of C. difficile diarrhea. The test shows
a low sensitivity (48–59%) but a high specificity (95–96%).
■ Stool cultures, however, are not useful due to the presence
of
nontoxigenic strains of C. difficile in feces.

9. Treatment
 No treatment is necessary for asymptomatic carriers. Stoppage of
the use of causative antibiotics may be the only treatment necessary
for those with mild antibiotic-associated diarrhea
without fever, abdominal pain, or leukocytosis.
 This approach allows for reconstitution of the normal colonic
microflora and significantly reduces the risk of relapse.
 Patients with more severe diarrhea or colitis require treatment with
antibiotics.
 Metronidazole is the drug of choice.
 Vancomycin and bacitracin are also effective.
 More than 95% of patients respond to 10 days of treatment with oral
vancomycin, or oral or intravenous metronidazole.