Clinical use
Detection of Clostridium difficile and Clostridium difficile toxin.
Background
Changes in the gut flora 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). Almost all drugs with an antibacterial spectrum of activity have been implicated causally in AAD. The most frequently implicated drugs are those which have a marked effect on the microflora of the colon. These include broad spectrum beta lactams, cephalosporins, clindamycin and fluoroquinolones. The incidence of C. difficile infection has been shown to decrease once antibiotic therapy is controlled.
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. The most accurate diagnosis of pseudomembranous colitis is affected by endoscopic detection of colonic pseudomembranes or microabscesses in antibiotic-treated patients who are suffering from diarrhoea, and who have C. difficile and its toxins in their stools. The organism has been associated with outbreaks in hospitals and in extended care facilities for the elderly. It represents an important cause of hospital-acquired infection. C. difficile can be isolated from soil, hospital environments and both human and animal faeces. It is rarely found in the flora of normal adults, but up to 50% of infants may be colonised in the first few months, although disease is rarely present at this age. C. difficile infection is more common in the elderly. The reasons for this are not clear, although there is some evidence to suggest that these patients have a less effective natural barrier to infection. Elderly medical patients, those undergoing general surgery, oncology patients and those with chronic renal disease are at particular risk of infection by C. difficile.
Patient preparation
- Fluid/Bristol stool 5-7 specimens from all hospital patient greater than or equal to two years of age are tested for Clostridium difficile.
- Fluid/Bristol stool chart 5-7 samples from all community patients 65 years or older
- Fluid/Bristol stool chart 5-7 specimens from community patients less than 65 years if C.difficile is requested.
Specimen requirements
1 – 2 grams of Faecal Sample or ileostomy/colostomy sample in a sterile white or blue top universal
Minimum volume
1 – 2 grams
Limitations & restrictions
- If a patient tests positive for C. diff, they will not be re-tested by the laboratory within a 28-day period following this result.
- If a patient is negative for C. diff, 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. diff.
- 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. diff is rejected due to the above restrictions, but testing is required by the medical team, please contact a medical microbiologist to discuss this.
