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The woman went into strict isolation: Everyone entering her room donned a protective gown and gloves and rigorously washed their hands. Her medical equipment got special decontamination. All other patients in the ICU had their throats and groins tested regularly to see if the bug was spreading.

All seemed OK. The woman recovered, and went home on July 15.

Fast forward three weeks. Now a man with cancer has KPC despite never crossing paths with Patient No. 1. Ten days later, a woman with an immune disease fell ill, too. Both died of the infection.

Did they arrive carrying their own KPC bacteria, or did that first patient’s germ somehow escape into the hospital? Standard tests couldn’t tell. Segre, the geneticist, turned to DNA.

As bacteria multiply, mistakes appear and are repaired in their genetic code. Sequencing that genome allowed Segre to follow differences in single genetic letters like a trail of the germ’s transmission and evolution.

Sure enough, the KPC originated from the New York patient despite NIH’s precautions. Testing bacteria from the 17 additional patients who ultimately caught it shows the KPC was transmitted three separate times from Patient No. 1, and then spread more widely.

Even this sophisticated technology couldn’t prove exactly how transmission occurred. But it turns out that Patient 3 had been in the ICU at the same time as the New York woman and really was the next infected, silently carrying the bug longer before becoming sick. That was enough time for Patient 3’s infection to spread to Patient 2, who just got sick faster.

Meanwhile, NIH was making big changes. All the ICU patients underwent more invasive testing, using rectal swabs, to check for silent germ carriers. A new wall created a separate ICU to house them. Doctors, nurses, even janitors assigned there could work nowhere else, and monitors were paid to make sure everyone followed infection-control rules.

Yet a patient a week was either becoming infected or found to be a silent carrier of the same KPC strain.

“Honestly, we were very scared at that point,” Segre recalled.

Test after test never found the bug on hospital workers’ hands. Tainted objects like the ventilator couldn’t be ruled out _ but NIH adopted more complex and expensive decontamination, using robot-like machines to spray germ-killing hydrogen peroxide into the tiniest of crevices in all affected rooms and equipment.

Still, November brought more bad news: The outbreak strain had escaped the ICU, as two patients who’d never been there now were carrying it. A new isolation room was built, and all 200-plus patients in the hospital started undergoing rectal testing.

The outbreak now is over, the last carrier found in December. But NIH isn’t dropping its guard. The isolation room remains, used every time one of the seven outbreak survivors returns to the hospital for their ongoing research studies _ because they still carry the strain. Those rectal tests continue, hospital-wide once a month, to be sure no new KPC strain sneaks in.

Bacterial sequencing is becoming fast and cheap enough for most large hospitals to use during tough outbreaks, said Dr. Lance Peterson, microbiology and infectious disease director at NorthShore University HealthSystem in Evanston, Ill.

But another lesson is how much it takes to guard against these bugs sneaking in in the first place. Peterson said his hospital does weekly rectal testing of every ICU patient as a precaution.

Story Continues →