His research has focused on organisms associated with bacterial vaginosis, a common but little-understood condition that increases the risk of preterm birth, pelvic inflammatory disease, HIV and other sexually transmitted diseases. Dr. Fredricks’ team also studies the impact of microbial communities on the outcomes of patients who receive blood stem cell transplants. His research shows that the makeup of gut bacterial populations can vary significantly among patients after antibiotic treatment, and analysis of these patterns might help predict the risk of graft-vs.-host disease, a potentially deadly transplant complication. He leads the Microbiome Research Initiative, a cross-disciplinary effort at Fred Hutch to deepen understanding of the effects of microbial communities on human health.