Inhibition of binding of Clostridium difficile toxin by steroids

No detectable inhibition of binding of Clostridium difficile toxin to human erythrocyte lysate was found with alpha-D-(+)-fucose, 1-(-)-fucose, ribose, arabinose, mannose, galactose, xylose, galactosamine, glucosamine, mannosamine, N-acetyl glucosamine, N-acetyl galactosamine, N-acetyl mannosamine, N-acetyl neuraminic acid, lactose, sucrose, lactulose, neuraminidase, saponin, or amantadine. Inhibition was found, however, with a number of sterols and bile acids. In general, bile acids were more active than cholesterol and related compounds. When the bile salts were added greater than or equal to 10 min after exposure to toxin, inhibition was no longer observed. These results suggest that the membrane receptor for C. difficile toxin is not likely to be a carbohydrate component. On the other hand, the inhibitory activity by steroids suggests that a lipid component may play an important role in toxin binding.