Vaccination with parenteral toxoid B protects hamsters against lethal challenge with toxin A-negative, toxin B-positive clostridium difficile but does not prevent colonization.

Toxin A has historically been regarded as the primary virulence determinant in Clostridium difficile infection, but naturally occurring toxin A-negative, toxin B-positive (A-/B+) C. difficile strains are known to be virulent. To determine the role of toxin B in these strains, we immunized hamsters with a toxoid prepared from purified toxin B to determine whether they would be protected from lethal challenge with an A-/B+ strain of C. difficile.