An unusual method for producing antibiotics may help solve two urgent global problems: the rise in infections that resist treatment with commonly used drugs and the lack of new antibiotics to replace ones that no longer work.
The method, which extracts drugs from bacteria that live in dirt, has yielded a powerful new antibiotic, researchers reported in the journal Nature on Wednesday. The new drug, teixobactin, was tested in mice and easily cured severe infections, with no side effects.
Better still, the researchers said, the drug works in a way that makes it unlikely that bacteria will become resistant to it. And the method used to make the drug has the potential to unlock a trove of natural compounds to fight infections and cancer, molecules previously beyond scientists’ reach because the microbes that produce them could not be grown in the lab.
Teixobactin has not been tested in humans, so its safety and effectiveness are not known. Studies in people will not begin for about two years, according to Kim Lewis, senior author of the article and director of the Antimicrobial Discovery Center at Northeastern University in Boston.
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Those studies will take several years, so even if the drug passes all the required tests, it will not be available for five or six years, he said during a telephone news conference Tuesday. If it is approved, he said, it will probably have to be injected.
Experts not involved with the research said the technique for isolating the drug had great potential. They also said teixobactin looked promising but expressed caution because it has not been tested in humans.
Dr. William Schaffner, an infectious-disease specialist at Vanderbilt University, called the research “ingenious” and said: “We’re in desperate need of some good antibiotic news.”
Regarding teixobactin, he said: “It’s at the test-tube and the mouse level, and mice are not men or women, and so moving beyond that is a large step, and many compounds have failed.” He added: “Toxicity is often the Achilles’ heel of drugs.”
Drug-resistant bacteria infect at least 2 million people a year in the United States and kill 23,000, according to the Centers for Disease Control and Prevention (CDC).
The World Health Organization (WHO) warned last year that such infections were occurring worldwide and that drug-resistant strains of many diseases were emerging faster than new antibiotics could be made to fight them.
But disease-causing organisms have become resistant to many existing drugs, and there has been a major obstacle to finding replacements, Lewis said: About 99 percent of the microbial species in the environment are bacteria that do not grow under usual laboratory conditions.
Lewis and his colleagues found a way to grow them. The process involves diluting a soil sample — the one that yielded teixobactin came from “a grassy field in Maine” — and placing it on specialized equipment. The secret to success is then putting the equipment into a box full of the same soil the sample came from.
“Essentially, we’re tricking the bacteria,” Lewis said.
Back in their native dirt, the bacteria divide and grow into colonies. Once the colonies form, Lewis said, the bacteria are “domesticated,” and researchers can scoop them up and start growing them in Petri dishes in the laboratory.
Teixobactin is the most promising candidate isolated from 10,000 strains of bacteria the researchers screened. In test tubes, it killed various types of staph and strep, anthrax and tuberculosis. Tested in mice, it cleared strep infections and staph, including a strain that was drug-resistant.
Teixobactin attacks bacteria by blocking fatty molecules needed to build cell walls, which is different from the way most antibiotics work. Those molecules are unlikely to change and make the microbes resistant, the researchers said.
But if resistance does occur, Lewis predicted, it will take a long time to develop.