Clostridium difficile infection (CDI) is a symptomatic infectious disease caused by the anaerobic, spore-forming bacterium called Clostridium difficileRecently CDI has become increasingly prevalent worldwide. The severity of the infection is also on the rise, meaning the requirement for a rapid and accurate method of diagnosis is more important than ever.

A recent study published in Intestinal Research has compared the accuracy and rapidity of three diagnostic methods:

  1. qPCR of toxin genes
  2. C. difficile toxin assay
  3. Culture for C. difficile

The qPCR reaction targeted the toxin B gene (tcdB), the critical component of all toxigenic C. difficile strains. It can additionally detect the epidemic 027/NAP1/BI strain which is associated with a higher mortality rate. The result is represented as toxigenic C. difficile positive or negative.


The C. difficile toxin assay tests stool samples with VIDAS® C. difficile toxin assay A and/or B. If the relative fluorescence value (RFV) is more than 0.37, the test is positive for CDI; an RFV of 0.13 to less than 0.37 means the result is equivocal, and if the RFV is less than 0.13, the test is negative.

For the culture method, stool samples were inoculated into ChromID™ C. difficile agar. The agar was then anaerobically incubated for 48-72 hours. Any suspected C. difficile cultures were then analysed by gram staining, spore staining, and/or a biochemical assay.

The study concluded the following:

We confirmed that real-time PCR of toxin genes is the most effective diagnostic method for accurate and early diagnosis of CDI. It also helps to diagnose hypervirulent CDI, such as ribotype 027 infection.

For more information, you can access the full article here.