Clostridium difficile Toxins, Redux

Richard T. Ellison III, MD


Journal Watch. 2010;30(21) 

In This Article

Abstract and Introduction


New data indicate that both toxin A and toxin B contribute to disease.


Although Clostridium difficile is known to produce two distinct toxins, A and B, the role of these toxins in inducing disease has been unclear. Initial work primarily implicated toxin A, but a more recent study performed with isogenic mutant strains of the pathogen suggested that toxin B is essential for virulence (JW Infect Dis Jun 2009, p. 41, and Nature 2009; 458:1176). To further explore this issue, investigators in the U.K. reassessed the role of each toxin by creating new stable isogenic mutant C. difficile strains that lacked toxin A (A–B+), toxin B (A+B–), or both (A–B–) and testing these strains in vitro and in vivo.

The A–B+ and A+B– strains both showed in vitro cytotoxic activity, and in a hamster model, both appeared to produce disease comparable to that seen with the wild-type (A+B+) parent strain. In contrast, the A–B– mutant showed no in vitro or in vivo activity.


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