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Common as Dirt: New Antibiotic May Conquer Superbugs

This black iChip was developed by researchers at Northeastern University to grow bacteria that usually don't grow in the lab. They used it to get a potentially very powerful new antibiotic from bacteria living in this soil samples, from a field in Maine. Slava Epstein / Northeastern University

A handful of dirt from a field has yielded what may be the first of a new family of antibiotics. Early tests suggest this one has the potential to be especially powerful, providing a new weapon against the growing threat of drug-resistant superbugs.

Scientists at Northeastern University in Boston and a small company called NovoBiotic Pharmaceuticals used a new method to find the compound, which appears to bypass the many different tricks that germs have for getting around the effects of antibiotics.

Tests in mice suggest it works to kill a wide range of bacteria, from staphylococcus to drug-resistant tuberculosis.

They've named it teixobactin. It comes from a soil-dwelling bacteria that usually doesn't thrive in the lab, so it hadn't been developed as a source of antibiotics.

"The compound is highly potent against a broad range of Gram-positive microbes, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE)," the company said in a statement.

And it came from an ordinary field in Maine. The new device may offer a way for scientists to harvest all sorts of different products from soil bacteria too shy to grow in most labs.

"What most excites me ... is the tantalizing prospect that this discovery is just the tip of the iceberg," said Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh.

Bacteria develop resistance to drugs quickly. Even before penicillin was introduced in 1943, staphylococcus germs had genes that would have made them resistant to its effects. Just nine years after tetracycline was introduced in 1950, a resistant strain of Shigella evolved. Methicillin-resistant Staphylococcus aureus (MRSA) evolved just two years after methicillin hit the market in 1960. The last new antibiotic to be introduced was ceftaroline, in 2010. It took just a year for the first staph germ to evolve that resisted its effects.

Image: Eleftheria terrae, a newly discovered soil bacterium dug up in a Maine field, has yielded a potentially powerful new antibiotic.
Eleftheria terrae, a newly discovered soil bacterium dug up in a Maine field, has yielded a potentially powerful new antibiotic. William Fowle / Northeastern University

"We desperately need new antibiotics," said Allan Coukell, senior director for health programs at the Pew Charitable Trusts. "We have increasing numbers of infections that cannot be treated with existing drugs."

"[Patients] are having to stay in the hospital, undergo other procedures, and, unfortunately, they are dying because we don't have new, effective antibiotics," added Amanda Jezek, vice president of public policy and government relations at the Infectious Diseases Society of America.

The Centers for Disease Control and Prevention says more than two million people are infected by drug-resistant germs each year, and 23,000 die of their infections. The biggest killer by far in the U.S. is diarrhea-causing C. difficile.

Near-untreatable cases of diarrhea, sepsis, pneumonia and gonorrhea are infecting millions more globally, the World Health Organization says.

Many new antibiotics are found in microbes and especially fungi and bacteria from dirt. They use them to fight off other microbes. The original antibiotic, penicillin, comes from Penicillium, a fungus found just about everywhere, including in soil.

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And while researchers know that any sample of dirt is likely to yield a wealth of bacteria, many just won't grow in the lab. That makes it hard to get a large enough sample to pull antibiotics from.

Kim Lewis of Northeastern and a team of colleagues came up with a new way to grow bacteria. It's called an iChip and it allows the bacteria to grow in their natural environment. They screened 10,000 different types of bacteria and found an especially promising one called Eleftheria terrae.

Lab tests showed it makes a compound that is great at killing other bacteria. It breaks down their protective cell walls and stops the rebuilding process. But it doesn't break down the type of cell envelopes that Gram-negative bacteria make, so it's unlikely to work against most strains of E. coli, for example, the vibrio bacteria that cause cholera or the Yersinia bacteria that cause plague. E. terrae is itself a Gram-negative bacteria.

It also doesn't appear to damage the cells of mammals. Tests in mice showed it could cure infections without causing harm. And it seems impervious to the various mutations that bacteria can use to resist its deadly effects.

The researchers tried several ways to get bacteria exposed to teixobactin to mutate but they did not. That probably won't last forever, but it could take decades for resistant mutants to evolve, Lewis and colleagues say.

"It is likely that additional natural compounds with similarly low susceptibility to resistance are present in nature and are waiting to be discovered," they wrote in their report, published in the journal Nature.

It would be years before this compound could become a new drug. Many tests are needed, and there are many ways for an experimental drug to fail.

Jezek says antibiotics are an especially problematic area because there's not much profit in making them.

"We are seeing companies pulling back from doing antibiotic development in part because the science is very difficult and the development costs are high," she said. "At the same time, the profit margins are very low."

People only take antibiotics for a few days, usually — unlike heart disease drugs or pain relievers that are taken for decades. "It just has created a really unique, really challenging business model," Jezek said.

This study points to a new way to find new antibiotics literally lying around, waiting to be discovered.