While antibiotics have done inestimable good to humankind over the last seventy years, there are several drawbacks to using antibiotics that, until recently, have been overlooked. The human microbiome, which consists of the trillions of bacteria that reside in each person's body, is essential to good health. Specifically, the body contains and requires both "good" and "bad" bacteria. It is when the proper equilibrium between the "good" bacteria and the "bad" bacteria is disrupted that a number of health issues can emerge. Nonetheless, antibiotics indiscriminately kill both the "good" and the "bad" bacteria, so each course of antibiotics should be followed by a treatment that _______.