Two large, prospective, multicenter, double-blind, randomized clinical trials (13, 21) have compared fidaxomicin to vancomycin; fidaxomicin demonstrated noninferiority to vancomycin in terms of cure rates, with one of these studies demonstrating a lower rate of recurrent infections when patients with the potentially virulent NAP-1 strain of C. difficile were excluded. This evidence concerns the gene CTNNBL1 and infection.