 28 healthy volunteers who gave informed consent were enrolled to participate in a study to determine the efficacy of prophylactic rifaximin in preventing diarrheal illness following challenge with C. jejuni, strain CG8421. Volunteers were screened for inclusion and exclusion criteria and were admitted to the inpatient unit of the Center for Immunization Research at Johns Hopkins University. Volunteers were treated with rifaximin or placebo in a double blind manner for four days, beginning the day prior to challenge. On the day of challenge, the volunteers were given 5x105 C. jejuni with bicarbonate buffer and were then monitored and treated for any symptoms. Stools were cultured daily for the excretion of C. jejuni and all subjects were treated with antibiotics to insure that the challenge strain has cleared prior to to discharge. Subjects were followed for six months following the inpatient phase to detect adverse events following the study. 