The Washington Post: How these biomedical detectives identified the dreaded new superbug in U.S.

June 6 at 9:43 AM

Microbiologist Patrick McGann knew he had identified a dangerous germ. He just didn’t know how dangerous.

His job at the Walter Reed Army Institute of Research in Silver Spring is to prevent outbreaks of new pathogens in the U.S. military’s sprawling health-care system. In mid-May, a colleague found a strain of bacteria from a 49-year-old woman in Pennsylvania that had tested positive for resistance to a drug called colistin, the antibiotic of last resort.

McGann wasn’t yet alarmed. Sometimes mutations occur spontaneously that make bacteria resistant to an antibiotic. It would be a completely different problem, though, if the bacteria turned out to carry a certain colistin-resistance gene, called mcr-1, discovered in China late last year.

But that required deeper molecular testing. McGann asked his research team to do an initial test for the presence of the resistance gene. He was on Metro’s Red Line, headed back to the lab from a meeting, and wasn’t expecting the bombshell that followed.

On May 18 at 12:32 p.m., research technician Ana Ong texted him to say the strain of E. coli bacteria tested positive for the mcr-1 gene.

Stunned, McGann texted back: “You’re s——- me??” And then, realizing what the discovery meant, he didn’t wait for her reply.

“Onto the sequencer ASAP,” he wrote back, referring to the labor-intensive, round-the-clock effort that would have to come next to sequence the bacteria’s entire genome.

“We had to drop everything else to get this done,” he explained later. “When [the test] came back positive, all hell broke loose.”

Sequencing was the only way to answer the most critical question: How easily could the gene spread?

For infectious disease experts, the nightmare scenario is for the gene to spread to multidrug-resistant bacteria that cannot be killed by anything except colistin. That would make them invincible to any antibiotic, unstoppable by the most life-saving drugs of modern medicine.

’This one popped up’

The gene mcr-1 was found in China last November, first in pigs and then in people, alarming the infectious-disease community as it was reported across Asia and Europe. By March, there were more reports from France, Switzerland, Brazil and Argentina.

Still, the gene is relatively rare. After the initial report from China, McGann’s team tested more than 3,000 antibiotic-resistant bacteria that had been collected from military facilities around the world. None contained the mcr-1 gene.

The long-dreaded news that bacteria with the mcr-1 gene have been detected in the United States is giving new urgency to measures throughout the federal government to find where else the gene might be lurking and to control its spread.

The Centers for Disease Control and Prevention estimates that drug-resistant bacteria cause 2 million illnesses and about 23,000 deaths each year in the United States. Many soldiers wounded during the Iraq war contracted a strain of bacteria that the media later dubbed “Iraqibacter.” The normally harmless bacteria, found in soil and on skin, got into wounds and caused stubborn bloodstream infections, many of them resistant to many types of antibiotics. After about 2007, colistin was often one of the most effective treatment options available, McGann said.

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