Study of Antibiotic-induced Vaginal Yeast Infections in Healthy Women

Study Summary

Background: \- Vaginal yeast infections are caused by a fungus called Candida. Candida can live harmlessly in the vagina, but most women will have symptoms from a vaginal yeast infection at some point during their life. Antibiotics increase the risk for yeast infections, but it is unclear why. They may disrupt the balance of healthy bacteria in the vagina. This could make it harder for the body to fight off yeast infections. Researchers will give healthy women a common antibiotic or a placebo. They will study how the antibiotic affects bacteria and yeast in the vagina and other parts of the body. This will let researchers study the normal changes of healthy bacteria and yeast over time. Objectives: \- To see how the study drug changes healthy bacteria in the vagina, and how these changes may increase the risk for yeast infections. Eligibility: \- Healthy women ages 18 to 40 who are not allergic to penicillin. Design: * Participants will be screened with medical history, physical exam (including vaginal exam), blood tests and tests for sexually transmitted diseases. * Participants must take birth control pills for at least 3 months before, and during the study. * Participants will take the study antibiotic or placebo for 10 days. * Participants will have 7 study visits over 3 months. Visits will be timed around participants menstrual cycles. * At the visits, participants will answer questions about their health and undergo tests. These may include swabs of the vagina, mouth and skin as well as blood tests. Vaginal fluid, saliva and urine will also be collected. * Between visits, participants will collect stool and vaginal samples at home and bring them to the next clinic visit.