 Our goal is to assess the safety and tolerability of LGG when administered to healthy adult volunteers twice a day. Assessment of safety will be determined by vital sign measurements, physical examinations, clinical laboratory tests, and from the incidence and severity of adverse events that occur during study participation. Additionally, we will assess whether LGG colonizes the throat andor gastrointestinal tract of healthy adult volunteers and assess the effect of LGG on the bacteria that normally live in the throat and GI tract by using culture-independent techniques. Volunteers enrolled in this study will also be invited to participate in a companion genetic study that will investigate the host immune response to the bacteria in LGG. 