In 2011, the NIH Clinical Center had a cluster of infections of a pathogen that tops the CDC's list of urgent threats: antibiotic-resistant Klebsiella pneumoniae. This bacteria, which can cause bloodstream and other infections, has recently developed resistance to the class of antibiotics known as carbapenems. The outbreak at NIH started with a single infected patient who was discharged weeks before any other cases were detected. This story of antibiotic-resistant infections is becoming more common around the world, and is especially dangerous in hospitals. Dr. Julie Segre, a senior investigator at the National Human Genome Research Institute, discuses how the outbreak was traced using state-of-the-art DNA sequencing.