Target and mechanism of antibacterial drug fidaxomicin (Dificid) discovered. Scientists have determined the molecular target and mechanism of the antibacterial drug fidaxomicin (Trade name Dificid). Fidaxomicin was approved in 2011 for treatment of the CDC 'urgent threat' bacterial pathogen Clostridium difficile (C. Diff) and currently is one of two front-line drugs for treatment of C. Diff. Source 7c.