Clostridium difficile - diagnostics in the stool

Thanks to its high degree of stability and sensitivity in comparison to toxin detection alone, the C. difficile-specific enzyme „glutamate dehydrogenase” (GDH) works very well as a screening test. The enzyme is produced by both toxigenic as well as by non-toxigenic strains. The negative predictive value of the GDH tests is 98-100 %. In case of a negative GDH test, no further confirmation tests are required. A C. difficile infection can be ruled out here with the highest degree of probability.

If the GDH test is positive, the toxin A/B test will automatically follow. If the toxin detection test is also positive, this is proof of an infection with a toxin-producing C. difficile strain (CDI).

In the constellation of a positive C. difficile GDH test and a negative C. difficile toxin test, this may be attributable to C. difficile strains with a lacking or low toxin formation. Likewise, overly long transport times and/or improper storage of samples can also lead to a reduction in toxin, thereby resulting in false negative test results for detecting the toxin. In such cases, clinical aspects should be taken into account when deciding on therapy. If there is any doubt, further stool samples can be sent in for analysis at any time.

If required, detection using cultures is possible, such as when there is a particularly severe clinical progression of the condition in a case where pathogen typing and/or antibiotic testing (metronidazole and vancomycin) are to be performed.

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PLEASE NOTE: A diagnosis of Clostridum difficile infections (CDI) is only meaningful when there are corresponding clinical symptoms with unformed, watery or liquid stools.

Pathogen, prevalence and path of infection
Clostridium difficile is an obligate anaerobically growing, Gram-positive, rod-shaped bacterium with the ability to form aero-tolerant spores. This pathogen is the most frequent cause of nosocomial diarrhoea. 1-5 % of the normal population is asymptomatically infected with this pathogen, especially children, the elderly and hospital patients. The spread of C. difficile takes place via faecal-oral smear infection.

Clinical picture
The disease is caused by endotoxin A and cytotoxin B, which are produced by pathogenic („toxigenic”) strains of the bacteria. The toxins cause damage to the intestinal cells, leading to diarrhoea and colitis.

Preventive measures
Following positive identification of this infection, the patient should be housed in a single room, if possible, with its own bathroom, since patients with C. difficile-induced diarrhoea excrete vegetative bacteria and spores of the pathogen that contaminate the environment. If necessary, cohort isolation may be carried out.

The hospital staff should also employ barrier measures (protective gowns, disposable gloves, etc.) and perform appropriate disinfection and surface cleaning.


If required, detection using cultures is also possible, such as when there are particularly severe clinical progressions in cases where pathogen typing and/or antibiotic testing (metronidazole and vancomycin) are to be performed.

Quantity: The stool sample tube should be approx. half filled.
Storage: The samples should be immediately transported to the laboratory and kept refrigerated until they are retrieved (at most 3 days at 2-8 °C).

Rectal swabs cannot be processed.

PLEASE NOTE: In the event of a negative result, persisting suspicions and lack of proof of any other pathogen, the test is to be repeated.

Treatment and prophylaxis
metronidazole (4 x 250 mg or 3 x 500 mg orally/i.v.) for 10 days.
Vancomycin (4 x 125 mg orally) for 10 days.
Fidaxomicin (2 x 200 mg orally) for 10 days.

Relapses are not rare (approx. 10-20 %), especially in elderly patients, in patients still receiving antibiosis and in cases of chronic gastro-intestinal diseases and severe underlying diseases.

The treatment of the first relapse should be the same as for the initial disease.

Obligation to report
PLEASE NOTE: Pursuant to sec. 6 (1) (5a) of the German Infection Protection Act (IfSG), the attending physician is only required to report patient names only when the course of the disease is severe. For example, serious clinical conditions, such as toxic megacolon and pseudomembranous colitis are notifiable.

In addition, pursuant to sec. 6 (3) IFSG, the attending physician is required to report an increased incidence of nosocomial infections, though not patient names, if there are more than 2 affected patients at the same time and place.

Literature and source

The European Society of Clinical Microbiology and Infectious Diseases (ESCMID): Update of the treatment guidance document for Clostridium difficile-infection (S. B. Debast, M. P. Bauer, E. J. Kuijper and on behalf of the Committee) The

European Society of Clinical Microbiology and Infectious Diseases (ESCMID): Data review and recommendations for diagnosing Clostridium difficile-infection (CDI) (M. J. T. Crobach, O. M. Dekkers, M. H. Wilcox and E. J. Kuijper)

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