Clostridium difficile infection is a major health care challenge in terms of patient and economic consequences. For the patient, it is a morbid and sometimes a life-threatening iatrogenic complication of antibiotic treatment. In the United States, the provider's institution may face financial penalties, because the Centers for Disease Control and Prevention views this as an iatrogenic health care-associated complication that may not be reimbursable by the Centers for Medicare and Medicaid Services; this has resulted in substantial incentives for new approaches to prevention and treatment.