XPECT Clostridium difficle Toxin A/B Test

Code: R24650 

Remel Xpect™ Clostridium difficile Toxin A/B test kit is a rapid in vitro immunochromatographic test for the direct, qualitative detection of Clostridium difficile Toxin A and/or B in human fecal specimens from patients suspected of having Clostridium difficile-associated disease (CDAD).  The test is intended for use as an aid in diagnosis of CDAD.  The test can also be used for confirmation of toxigenic C. difficilefrom Brain Heart Infusion Broth (CMM0225/BO0366) culture.

Additional information can be obtained by downloading the Xpect Clostridium difficle Toxin A/B IFU(706KB) in PDF format.

Background
C. difficile was first described in 1935, but it was not until 1977 that links were made between the organism and disease.  C. difficile is a toxin-producing, spore-forming anaerobic gram-positive bacillus.  The clinical presentation of C. difficile infection includes, in increasing order of severity, asymptomatic carriers, antibiotic-associated colitis, pseudomembranous colitis (PMC), and fulminant colitis¹.  A reduction of the normal microbial flora in the colon, usually caused by antibiotic therapy, allows overgrowth of C. difficile. Symptoms of antibiotic-associated colitis usually begin four to ten days after antibiotic treatment has begun.

Most pathogenic strains of C. difficile produce two toxins, Toxin A (enterotoxin) and Toxin B (cytotoxin), which are the main virulence factors for the organism.  There appears to be a cascade of events, which result in the expression of the activity of these toxins.  Toxin A is mildly cytopathic but induces large fluid shifts and mucosal inflammation.  Toxin B is intensely cytopathic but its role in the disease process is not clearly understood.  Variant strains which are Toxin A-negative, Toxin B-positive are known to exist, are fully pathogenic, and capable of producing the full spectrum of disease.  The prevalence of these variant strains varies widely by institution and geographic location ^2-7.

C. difficile-associated disease (CDAD) primarily occurs in hospitalized patients^8,9. Individuals with CDAD shed spores in the stool, which can survive for as long as five months in the environment.  Clinical and pathological features of CDAD are not easily distinguished from those of other gastrointestinal diseases, including ulcerative colitis, chronic inflammatory bowel disease, and Crohn’s disease.  Infection with toxigenic C. difficile is a potentially life-threatening disease process; however, when properly treated, patient mortality rates are low.  Thus, rapid diagnosis, allowing clinicians to initiate appropriate therapy and implement adequate measures to control nosocomial spread, is important.

Material supplied

Principle of the test
The Xpect Clostridium difficile Toxin A/B test is a qualitative immunochromatographic assay that detects C. difficile Toxin A and Toxin B in stool specimens or cultures of toxigenic C. difficile. In performing the test, a specimen is first diluted with Specimen Diluent to help solubilize the toxins. A portion of the diluted sample is then mixed with a volume of Conjugate 1 containing antibodies to Toxin A and Toxin B coupled to colored microparticles, plus a volume of Conjugate 2 containing biotinylated antibodies to Toxin A and Toxin B. A volume of this mixture is transferred to a test device having immobilized streptavidin as a test line and goat anti-immunoglobulin antibody as a control line. Immunocomplexes of toxin and conjugated antibodies form a visible band as they flow across the test line.  Excess colored particle conjugates form a visible band at the control line to document that the test is functioning properly.

Materials required but not supplied
(1) Stool specimen collection container(s), and (2) Timer.

Optional materials not provided:
(1) Specimen transport media, (2) Brain Heart Infusion Broth (CM0225/BO0366), and (3) Test tube rack.

References

1. Gerding, D.N., S. Johnson, L.R. Peterson, M.E. Mulligan, and J. Silva, Jr. 1995. Infect. Control Hosp. Epidemiol. 16:459-477.

2. Limaye, A.P., D.K. Turgeon, B.T. Cookson, and T.R. Fritsche. 2000. J. Clin. Microbiol. 38:1696-1697.

3. Alfa, M.J., A. Kabani, D. Lyerly, S. Moncrief, L.M. Neville, A. Al-Barrak, G.K.H. Harding, B. Dyck, K. Olekson, and J.M. Embil. 2000. J. Clin. Microbiol. 38:2706-2714.

4. Barbut, F., V. Lalande, B. Burghoffer, H.V. Thien, E. Grimprel, and J. Petit. 2002. J. Clin. Microbiol. 40:2079-2083. 

5. Johnson, S., S.P. Sambol, J.S. Brazier, M. Delmée, V. Avesani, M.M. Merrigan, and D.N. Gerding. 2003. J. Clin. Microbiol. 41:1543-1547.

6. Kato, H., N. Kato, K. Watanabe, N. Iwai, H. Nakamura, T. Yamamoto, K. Suzuki, S. Kim, Y. Chong, and E.B. Wasito. 1998. J. Clin. Microbiol. 36:2178-2182.

7. Johnson, S., S.A. Kent, K.J. O’Leary, M.M. Merrigan, S.P. Sambol, L.R. Peterson, and D.N. Gerding. 2001. Ann. Intern. Med. 135:434-438.

8. Wilkins, T.D. and D.M. Lyerly. 2003. J. Clin. Microbiol. 41:531-534.

9. Fedorka, D.P. 2002. Clin. Microbiol. Newsletter. 24:76-79.