The primary objective of this study is to determine whether giving SBI as a medical food starting with maintenance of health in the management of chronic loose and frequent stools in IBS-D subjects with SIBO after successful treatment with rifaximin can lead to more prolonged duration of benefit and delay symptom recurrence. SBI is the main ingredient in EnteraGam™, an orally administered prescription medical food for the dietary management of patients with enteropathy or chronic loose or frequent stools, including patients with IBS-D.