Three weeks after returning from their trip, unlike W.D. who is free of intestinal symptoms, B.D….

Three weeks after returning from their trip, unlike W.D. who is free of intestinal symptoms, B.D. continues to have episodes of loose stools and abdominal discomfort, for which she seeks medical attention. On physical examination, her vital signs are stable and she is afebrile. The physician believes her symptoms are consistent with the postinfectious irritable bowel syndrome (PI-IBS). Why is B.D.’s history and clinical presentation consistent with this diagnosis, and what therapies can be recommended to manage these symptoms?