The present invention provides isolated polypeptides comprising a fragment of the amino acid sequence of SEQ ID NO:1, or a variant, derivative or fusion thereof, which is capable of binding specifically to and lysing cells of Clostridium difficile, wherein the polypeptide exhibits greater lytic activity on cells of Clostridium difficile than the polypeptide of SEQ ID NO: 1. The invention further provides means for producing the same, methods for killing bacterial cells such as cells of Clostridium difficile, as well as methods for diagnosing, treating and preventing diseases and conditions associated with infection of the same.
