Study to Assess Inhibition of Spore Production in Patients With C. Difficile Infections: Fidaxomicin Versus Vancomycin

Inclusion Criteria: * 18 years of age and above * First diagnosis of C. difficile infection * Treatment for C. difficile infection less than 24 hours * Female subjects must be nonpregnant, nonlactating, and either postmenopausal for at least 1 year, surgically sterile (i.e., documented tubal ligation or hysterectomy) for at least 90 days, abstinent, or agree to use 1 of the following forms of contraception from the time of signing the Informed Consent form (ICF) until 30 days after leaving the study site: a nonhormonal intrauterine device (IUD) with spermicide, female condom with spermicide, contraceptive sponge with spermicide, diaphragm with spermicide, cervical cap with spermicide, a male sexual partner who agrees to use a male condom with spermicide, or a sterile sexual partner. Exclusion Criteria: * History of hypersensitivity to fidaxomicin or vancomycin * Pregnant or breast-feeding * Active treatment with other therapies with activity against C. difficile * Receiving any peristaltic agents * Medical history including ulcerative colitis or Chron's disease * Ordered to be nothing by mouth or cannot swallow the study medication * Participation in another clinical research study utilizing pharmacological treatment within 1 month or five half-lives of the medication whichever is longer * Any other reason felt by the investigator to potentially affect the outcomes of the study