A MacConkey agar culture plate that cultivated anaerobic Klebsiella pneumoniae… (/Courtesy CDC )
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 hospital.
With some 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 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.
Later this year, the CDC is launching a program in 10 cities, including Baltimore, to watch for hospital-borne outbreaks of Klebsiella and related superbugs. CDC staff will review hospital records, Kallen said, and hospital labs will be asked to report any antibiotic-resistant bacteria to the CDC.
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.
After the patient was discharged the next month, Palmore and her staff thought these measures had worked. There were no signs that the bacteria had spread.
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.
The pattern baffled Palmore. If the superbug had jumped from the New York patient, it should have showed up sooner in three new patients.
But by reading the bacteria’s DNA, scientists at the NIH’s National Human Genome Research Institute saw that the organisms from patients No. 2 and 3 were so closely related — differing at just one or two genetic letters out of 6 million — they had to have come from the New York patient.
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. Details of the genetic analysis and the outbreak were published Thursday in the journal Science Translational Medicine.
“It still got out, after only two 24-hour periods in the ICU,” Palmore said. “During that time, the bacteria were transmitted to three people.”