Researchers unraveled a medical mystery that left six patients dead last year at the National Institutes of Health's elite research hospital, demonstrating that gene sequencing can help in the fight against hospital-acquired infections.

The NIH researchers' sleuth work—they stalked a deadly strain of antibiotic-resistant Klebsiella pneumonia through 18 patients at the agency's 243-bed Clinical Center in Bethesda, Md.—was detailed in a study published online Wednesday by Science Translational Medicine. The scientists sequenced...