Clostridium difficile

Test code: B0037 - Qualitative detection of Clostridium difficile bacteria by polymerase chain reaction.  This assay differentiates pathogenic and non-pathogenic strains of C. difficile by detecting the toxin producing genes.

Clostridium difficile is a gram positive, anaerobic, spore forming motile rod bacterium that commonly inhabits the intestinal tract of many mammalian species, reptiles and birds. It is also found in the environment. The bacterium is a highly diverse organism, with more than 400 unique types, and has several virulence factors. Exotoxin A and B are the most significant factors, and bacterial production of exotoxins is correlated with pathogenicity of individual strains of C. difficile. Toxin A is an enterotoxin, promoting fluid exudation from the intestinal mucosa, and acts synergistically with the cytotoxic toxin B through attachment to specific receptors on the surface of enterocytes. The combined action of these toxins results in necrosis of superficial epithelium and edema in affected areas of intestine.

The organism is an important cause of enteric disease in laboratory rodents and horses. Hamsters, guinea pigs and mice may be affected by pseudomembranous colitis induced by antimicrobial therapy. In neonatal foals, C. difficile has been associated with hemorrhagic necrotizing enterocolitis and diarrhea. The lack of an established intestinal microflora may make foals more susceptible to colonization by this bacterium. Adult horses may develop typhlocolitis and outbreaks of nosocomially acquired diarrhea have been reported (Donaldson and Palmer, 1999; Madewell et al., 1995; Perrin et al., 1993).

C. difficile has also recently been implicated as a cause of typhlocolitis in nursing piglets, chronic diarrhea in dogs and enterotoxemia in ostriches.

In clinically normal patients, an established intestinal microflora is thought to competitively prevent proliferation of C. difficile and subsequent toxin attachment. Alteration of intestinal microbial balance with antibiotic use and increased exposure to the organism in a hospital setting allows C. difficile to colonize the gut in susceptible individuals.

Bacterial culture of C. difficile is not highly sensitive and does not differentiate the pathogenic and non-pathogenic strains. Specific tests for C. difficile toxins used in the diagnostic laboratory include cell culture, which relies on the presence of biologically active toxin, and an ELISA assay which detects immunologically active toxin that may or may not be biologically active.

PCR detection of C. difficile is highly sensitive and can discriminate between toxigenic and nontoxigenic strains of the organism by detecting its toxin producing genes.

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of C. difficile infection.
• Ensure that animal groups or populations are free of this bacterium
• Early prevention of spread of this bacterium
• Minimize human exposure to this bacterium
• Safety monitoring of biological products that derive from animals

References:
Donaldson, M.T. and Palmer, J.E. (1999) Prevalence of Clostridium perfringens enterotoxin and Clostridium difficile toxin A in feces of horses with diarrhea and colic. J. Am. Vet. Med. Assoc. 215:358 361.
Madewell, B.R., Tang, Y.J., Jang, S., Madigan, J.E., Hirsh, D.C., Gumerlock, P.H. and Silva, J. (1995) Apparent outbreaks of Clostridium difficile associated diarrhea in horses in a veterinary medical teaching hospital. J. Vet. Diagn. Invest. 7:343 346.
Perrin, J., Cosmetatos, I., Gallusser, A., Lobsiger, L., Straub, R. and Nicolet J. (1993) Clostridium difficile associated with typhlocolitis in an adult horse. J. Vet. Diagn. Invest. 5:99 101.

Specimen requirements: Rectal swab or 1 ml feces, shipped overnight at room temperature.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative PCR

Normal range: Nondetected