- Subjects on multiple/combination immunosuppressive regimens including high dose corticosteroids, calcineurin inhibitors, lymphocyte depleting biologic agents, anti-tumor necrosis factor agents. Subjects on a stable dose of a SINGLE immunosuppressive agent like steroids, rituximab, infliximab, other anti-TNF agents, with approval of the treating physician may be enrolled. These subjects may be at greatest risk of complications and hospitalization if another relapse of CDI occurs and may benefit.