As a deadly infection, untreatable by nearly every antibiotic, spread through the National Institutes of Health’s Clinical Center last year, the staff resorted to extreme measures. They built a wall to isolate patients, gassed rooms with vaporized disinfectant and even ripped out plumbing. They eventually used rectal swabs to test every patient in the 234-bed hospital.

Still, for six months, as physicians fought to save the infected, the bacteria spread, eventually reaching 17 gravely ill patients. Eleven died, six from bloodstream superbug infections.

The outbreak of the antibiotic-resistant bacteria known as Klebsiella pneumoniae was not made public until Wednesday, when NIH researchers published a scientific paper describing the advanced genetic technology they deployed to trace the outbreak.

This was “the proverbial superbug that we’ve all worried about for a long time,” said Tara Palmore, an infection control specialist at the Bethesda, Md., hospital.

With about 99,000 U.S. deaths attributed to hospital-borne infections annually, the NIH outbreak provides a stark case study of the dangers of the latest wave of hospital-bred bacteria and the extreme measures that hospitals must adopt to stem the rising superbug tide.

The NIH Clinical Center now screens every patient transferring from another facility for superbugs, tests every patient in the intensive care unit twice a week and screens every patient monthly.

“This was our introduction to antibiotic-resistant Klebsiella,” Palmore said. “We hoped we would never see it.”

Clinical Center spokeswoman Maggie McGuire said the hospital did not alert the public earlier because Klebsiella infections do not trigger mandated reports to the Centers for Disease Control and Prevention like other infectious diseases do, such as HIV.

She also downplayed such outbreaks as too common to be newsworthy.

“There are … hospital-acquired infections in almost every hospital in the country,” she said. “It’s happening everywhere.”

Nationwide, about 6 percent of hospitals are battling outbreaks of the class of superbugs known as carbapenem-resistant bacteria, which includes Klebsiella, said Alexander Kallen of the CDC.

These bacteria usually live harmlessly in our intestinal tracts, and they pose little or no threat to patients with healthy immune systems. But in patients with compromised immune systems, the bacteria can turn dangerous, gaining an enzyme that defeats even the most powerful antibiotics. That’s what happened at NIH.

The six patients who died of bloodstream Klebsiella infections had immune systems weakened by cancer, anti-rejection drugs given after organ transplants, and genetic disorders.

The CDC detected this type of antibiotic-resistant bacteria in 2000. “Since then, we’ve seen it spread across the country,” Kallen said, to 41 states.

At NIH, the superbug arrived in June 2011. Hours before a 43-year-old female lung transplant patient arrived from New York City, NIH nurses noted something startling in her chart: She was carrying an antibiotic-resistant infection.

Desperately wanting to contain the superbug, the NIH staff isolated the woman in the ICU. Staff members donned gowns and gloves before entering her room. Her nurses cared for no other patients.

But a few weeks later, Palmore was “horrified,” she said, when a second patient tested positive for the bacteria. A third and fourth soon followed. Those three patients died as the bacteria grew impervious to every known antibiotic – even experimental new drugs.

That meant two unsettling things, said Julie Segre, the scientist at NHGRI who led the DNA analysis. The bacteria had lingered for weeks unnoticed, either in the hospital or in the new patients; and the hospital’s infection control measures for the New York patient had failed.

With genetic evidence of a single-source outbreak, in mid-August the Palmore-led staff quickly rolled out the strict new measures.

Still, they found Klebsiella in patients, at a rate of about one per week.

“Every single time a new patient, a new case came to light, it felt like a failure,” Palmore said.

For treatment, the hospital staff resorted to colistin, a decades-old antibiotic that can severely damage kidneys. While it defeated the superbug in a few NIH patients, in at least four, the bacteria evolved so rapidly, it outran colistin, too. Those four died.

The strict infection-control measures eventually paid off. No new cases have occurred since January, she said. However, two Klebsiella-positive patients remain at the hospital.

To slow the spread of superbugs, hospitals and long-term care facilities such as nursing homes must be ever-vigilant, the CDC’s Kallen said. Although most hospitals can’t afford the extreme measures the NIH implemented, the CDC encourages hospitals to adhere to the basics, such as constant hand-scrubbing and isolation of infected patients.

Surveillance is key to stemming hospital-borne outbreaks, he said, especially in light of the lack of new superbug-fighting drugs in the pharmaceutical industry’s pipeline.

“We’re talking in the range of a decade before we have new antibiotics that might be able to help,” Kallen said.