Clinical use
Detection of Clostridium difficile (now called Clostridioides difficile) and Clostridium difficile toxin.
Background
Changes in the gut flora (microbiome) associated with broad spectrum antibiotics and chemotherapeutic agents can result in colonisation by C. difficile; it is the commonest identifiable cause of antibiotic associated diarrhoea (ADD). Most antibiotics have been implicated, but broad spectrum beta lactams, cephalosporins, clindamycin and fluoroquinolones are considered the highest risk. C. difficile infection (CDI) is a toxin mediated disease, transmitted via the faecal-oral route through the ingestion of spores. The production of two toxins A (enterotoxin) and B (cytotoxin) causes the characteristic mucosal damage consisting of plaque-like lesions leading to the formation of a pseudomembrane. Not all strains of C. difficile produce toxin, and therefore not all can cause illness.
The spectrum of disease ranges from a self-limiting mild diarrhoea, to the advanced and severe illness characteristic of pseudomembranous colitis. In some cases patients can present with ileus. Toxic megacolon and perforation are infrequent but serious complications.
Patients at particular risk for CDI are the elderly, those receiving chemotherapy or who have chronic renal disease.
C. difficile causes outbreaks in hospitals and in extended care facilities. It represents an important cause of hospital-acquired infection and therefore local infection control procedures should be followed in cases of CDI (please see HIC23)
The testing algorithm for C. difficile involves a combination of tests. The first, an immunoassay detects the presence of C. difficile in the sample via the detection of the glutamate dehydrogenase enzyme (GDH). The second, another immunoassay, detects the presence of the C. difficile toxin in the sample. In cases where GDH is detected but the toxin is not detected in the sample, a PCR test is undertaken to identify whether the C. difficile strain carries the toxin gene.
Patient preparation
The following patient populations are automatically tested for C. difficile on receipt of a stool sample which meets the definition of diarrhoea (Bristol stool type 5-7, i.e. stool which takes the shape of the container it is held in):
- All hospital inpatients aged ≥2 years
- All community patients ≥ 65 years of age
C. difficile will be tested if specifically requested for community patients <65 years of age on receipt of a stool meeting the consistency of Bristol stool type 5-7.
Specimen requirements
Diarrhoeal stool/ileostomy/colostomy sample (Bristol stool chart 5-7 types)
Minimum volume
1 – 2ml
Limitations & restrictions
- Formed stool (Bristol stool chart 1-4) is not tested for C. difficile
- If a patient tests positive for C. difficile, they will not be re-tested by the laboratory within a 28-day period following this result.
- If a patient is negative for C. difficile, the patient will only be retested a further two times within a 28-day period.
- Children under the age of 2 will not be tested for C. difficile.
- Bloodstained samples (more than 40% blood or visibly bloody) may produce false positive results.
Turnaround time
4 hours
Analysing laboratory
Microbiology Lab, James Cook University Hospital, Marton Road, TS4 3BW
Additional information
If a test for C. difficile is rejected due to the above restrictions, but testing is required by the medical team, please contact a medical microbiologist to discuss this.