HLA-DRB1 and clostridium difficile infection: Shen et al.17 identified two alleles in in the extended major histocompatibility complex (MHC; HLA-DRB1*07:01 and HLA-DQA1*02:01) that were associated with a reduction in CDI recurrence among 704 patients who achieved initial clinical cure with bezlotoxumab treatment in the MODIFY clinical trials.