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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 May13 2009). 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 w…