C.difficile infection: qualitative detection of GDH antigen and toxins (Toxin A +Toxin B) in faeces

Clostridium difficile is a spore-forming, Gram-positive, anaerobic bacterium that can be present asymptomatically in up to 5% of the healthy population. This carrier rate can increase up to 30% as a result of hospitalisation. C.difficile is considered to be responsible for approximately 25% of the diarrhoea associated with the consumption of antibiotics, including clindamycin, second- and third-generation cephalosporins, gyrase inhibitors, ampicillin, amoxicillin, and so forth.

Causes: Spores of the C. difficile bacteria can be passed out of the human body in stools and can survive for many weeks, and sometimes months, on objects and surfaces. If you touch a contaminated object or surface and then touch your nose or mouth, you can ingest the bacteria. The C. difficile bacteria do not usually cause any problems in healthy people. However, some antibiotics can interfere with the natural balance of normal bacteria in the gut that protects against C. difficile infection.

Symptoms:The most common symptoms include watery diarrhoea ( for several days) with abdominal pain, to which could be added loss of appetite, fever and weight loss in more severe infections. In addition to the diarrhoea symptoms, the disease can develop into pseudomembranous colitis (PMC), which requires urgent treatment with antibiotics effective against C.difficile (metronidazole, vancomycin) as the patient's life may be at risk. CDI-related mortality can be between 6% and 30%, especially if the patient suffers from PMC.

Glutamate dehydrogenase (GDH) is an enzyme produced by (toxigenic and non-toxigenic) strains of C.difficile in large quantities, thus making it an excellent marker for determining the presence of this microorganism. But the presence does not imply infection. C.difficile releases two high molecular weight toxins, toxin A and toxin B, which are the main virulence factors responsible for the clinical signs of CDI disease.

The Society for Healthcare Epidemiology of America (SHEA), the Infectious Diseases Society of America (IDSA) and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) propose the use of a two-step protocol for identifying toxigenic C.difficile involving an initial screening of the sample with a GDH test and, if the result is positive, use of a second test to detect toxins from C.difficile as not all strains of this microorganism produce them.

Operon offers the possibility of following this protocol recommended by some of the leading healthcare societies using its GDH and 2A-Bdiff tests.

Both, GDH and 2A-Bdiff tests are available in two formats:

- Stick format: the reactive strip itself packaged individually within an aluminium wrap. An additional test tube (or an 96-well microplate with flat-bottom) is required to deposit the extracted sample and run the test.

-Simple format: the reactive strip inside a plastic cassette. The extractions are added directly to the sample window that is marked with an arrow on the casing.

Both formats display the same features.