This is an exploratory, Phase IIa, open-label study assessing the safety, tolerability, and efficacy of incremental doses of MGB-BP-3 with 3 sequential groups of 10 patients with CDAD. Patients will be administered an oral dose of MGB-BP-3 for 10 days (Day 1 to Day 10). At the end of the treatment period, patients will be followed for up to 8 weeks to assess the incidence of disease recurrence.