In addition to the two major toxins of Clostridium difficile--toxins A and B, which represent the major virulence factors--a number of other putative virulence factors have been described. These factors include fimbriae and the ability to associate with gut cells/mucus, the production of a capsule, the secretion of a range of hydrolytic enzymes, the production of other toxins (such as an actin-specific ADP-ribosyltransferase by some strains), and the controversial possibility of the production of a second enterotoxin. The extent to which these additional putative virulence factors are involved in the pathogenesis of C. difficile-related gut disease remains to be elucidated.