In 2011, deadly, drug-resistant Klebsiella pneumoniae carbapenemase (KPC) spread through the NIH Clinical Center in Bethesda, Md., puzzling health experts and leaving 11 patients dead. This month, PBS explored the outbreak's path in a documentary entitled "Hunting the Nightmare Bacteria"—drawing on NIH's study of the outbreak.

• Want to see a preview of the documentary? Read more.

Anatomy of an outbreak: NIH battles KPC

Patient zero. A female patient suffering from complications resulting from a lung transplant is transferred from a New York hospital to NIH—she is admitted with a known case of KPC. NIH has never had a case of KPC before, and hospital officials discharge the woman only after they believe they have contained the bug.

Patient two. Several weeks later, a man hospitalized with a tumor tests positive for KPC. The two patients have no known link, and no crossover when it comes to time spent in the hospital, caregivers, and equipment.

KPC outbreak. Over the next few months, several more patients test positive for KPC and NIH creates a separate ICU for KPC patients. The old ICU is cleaned out and disinfected by robots before patients are moved back in, but KPC spreads beyond the ICU.

Failure to cure patients. Meanwhile, physicians try several combinations of antibiotics—even an experimental drug still in development—but, nothing works. Ultimately, 11 infected patients die.

The last patient. A year after the outbreak seems to have claimed all of its victims, a patient arrives at NIH suffering from complications related to a bone marrow transplant. He becomes infected with KPC and dies.

• Drug-resistant 'superbug' reported in 35 states

NIH officials respond to the outbreak

When patient zero was diagnosed with KPC, "[w]e immediately went on high alert, the equivalent of hospital epidemiology Def-con 5," according to the center's deputy director David Henderson. He added that the center implemented as many initiatives as possible "to prevent any further spread of the organism in the hospital," including using genetic analyses to try and understand the transmission sequence.

• Gene sequencing helps contain deadly hospital superbug

NIH researchers charted the outbreak's path by identifying:

• Whether a patient was in the same ward with an infected patient;
• Whether two patients shared a genetically similar KPC infection, even though they did not overlap at the center; and
• Whether patients did not overlap, but may have spread the infection another way—through a device or a staff member.

NIH officials say today they know KPC is still lurking in its clinical center.

"I think that we have to be extremely vigilant in the coming years, because of the increasing rise, the increasing prevalence of KPCs in the United States," NIH infectious disease specialist Tara Palmore says (Rockwood/Childress, "Frontline," PBS, 10/22).