Woman found to harbor infection resistant to antibiotic of last resort

Corrections and clarifications: An earlier version of this story misstated the extent of antibiotic resistance seen in a woman's E. coli infection.

For the first time, doctors have diagnosed an American with an infection that can't be treated with an antibiotic of last resort, an ominous development in the battle against antibiotic resistance, according to a new study.

The antibiotic, colistin, is used when infections become impervious to all other drugs, including a class of antibiotics called carbapenems. Colistin, which was approved in the 1950s, fell out of favor in the 1970s because of its toxicity. Doctors have resumed using it when nothing else works.

In the past six months or so, scientists have found bacteria that are resistant to colistin in more than two dozen countries, said study co-author Patrick McGann, a senior microbiologist at the Walter Reed National Military Medical Center in Bethesda, Md. Given the danger of colistin-resistant bacteria, doctors at Walter Reed decided to begin testing samples from the U.S.

"People have begun looking for it," McGann said. "And now that they're looking for it, they're finding it. It's only a matter of time before these bacteria start showing up."

The first patient with a colistin-resistant E. coli infection is a 49-year-old woman, who sought care for a urinary tract infection at a Pennsylvania clinic in April. Doctors sent her lab sample to the Walter Reed National Military Medical Center in Bethesda, Md., where researchers analyzed the bacteria's genes.

The good news was that the woman's infection was susceptible to a handful of antibiotics, including carbapenems, said study co-author Kurt Schaecher, service chief for the infectious disease lab at Walter Reed. That means her infection was treatable.

"We risk being in a post-antibiotic world," said Thomas Frieden, director of the Centers for Disease Control and Prevention, who wasn't involved in the new study, published Thursday in Antimicrobial Agents and Chemotherapy, published by the American Society of Microbiology. "The medicine cabinet is empty for some patients."

Health officials have warned for years of the growing danger of antibiotic-resistant "nightmare bacteria," which have evolved ways to avoid being killed by standard drugs. The problem is fueled by overuse of antibiotics, which are used not only in medicine but also food production.

One in three antibiotic prescriptions is unnecessary, the CDC announced last month. President Obama last year announced a National Action Plan for Combating Antibiotic-Resistant Bacteria to address the problem.

Although the problem is serious, the number of bacteria resistant to colistin is still relatively small in the U.S. and Europe, said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. McGann said the U.S. has a lower risk of superbugs than other countries, because doctors here prescribe antibiotics more prudently than in many places.

Antibiotics revolutionized medicine in the mid-20th century, making surgeries safer. If infections can't be treated by antibiotics, people could die from small wounds or minor surgery. Already, about 700,000 people a year die from resistant infections, according to the Review on Antimicrobial Resistance, a project commissioned by the British government, in collaboration with the Wellcome Trust. In the U.S. alone, 2 million people develop resistant infections each year and 23,000 die, according to the CDC.

Bacteria today are mutating faster than pharmaceutical companies are developing drugs to kill them. Because most people take antibiotics for a few days or a week, they aren't very profitable, giving drug companies little incentive to invest in them.

The last new class of antibiotics was discovered in 1984, according to a new report from the Pew Charitable Trusts.

"The major pharmaceutical companies have dropped many of their anti-infective programs over the last decade," said Peter Hotez, director of the Sabin Vaccine Institute at Texas Children’s Hospital Center for Vaccine Development in Houston. "We’re going to need new actors to take on programs of antimicrobial resistance, including small and midsize biotechs, non-profit product development partners and developing country manufacturers."

Two senators — Michael Bennet, D-Colo. and Orrin Hatch, R-Utah — have introduced legislation to speed up the approval of new antibiotics, called the Bennet-Hatch PATH Act. The bill would allow the Food and Drug Administration to expedite an antibiotic’s approval for an "identifiable, limited patient population," such as those with antibiotic-resistant infections, if the drug treats a serious or life-threatening condition and addresses an unmet need.

“This is terrifying news,” Bennet said in a statement. “We need new drugs to fight these antibiotic-resistant bacteria that pose serious and unique challenges to health care professionals."