The present invention relates to immunogenic compositions comprising isolatedClostridium difficileCDTb. In particular the isolatedClostridium difficileCDTb protein has been mutated to modify pore forming ability, to modify heptamerisation ability, or is a truncated CDTb protein with the signal peptide and the prodomain removed and also the receptor binding domain removed and/or the CDTa binding domain removed.The invention also relates to fusion proteins comprising a CDTa protein and a CDTb protein. Vaccines comprising such immunogenic compositions and therapeutic uses of the same also form part of the invention.
