A bucketful of Maine dirt could hold a key to fighting the growing global epidemic of drug-resistant infections.
That’s the hope of a team of researchers led by Northeastern University scientists who developed a novel way of growing soil bacteria in a lab, then discovered a new antibiotic in Maine soil that proved particularly effective against two deadly pathogens that sicken hundreds of thousands worldwide every year.
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Most promising of all, the quickly mutating pathogens were unable to develop resistance to the antibiotic, according to a study published this week in the journal Nature. The lack of resistance makes the antibiotic more effective over time in eliminating an infection.
“Our impression is that nature produced a compound that evolved to be free of resistance,” Kim Lewis, the lead researcher, said in a story on Northeastern’s website. “This challenges the dogma that we’ve operated under that bacteria will always develop resistance. Well, maybe not in this case.”
The potential superbug-buster came from soil taken from “a grassy field in Maine” – although it was unclear whether this was super-special soil or just the first success of a new technology that vastly expands the candidate pool for beneficial microbes.
A microbiologist involved in the research, Losee Ling, said in an interview with the Portland Press Herald that the team asked friends, family members and colleagues to send samples of dirt for testing, and the Maine soil was among that group. After screening thousands of bacterial colonies from submitted samples, the team of researchers identified 25 candidates for more exhaustive lab culturing and analysis.
In testing on mice, the antibiotic found in the Maine soil was effective against several pathogens – including the one that causes the increasingly common Methicillin-resistant Staphylococcus aureus, or MRSA, infections – but did not harm the mouse cells. It also broke down the bacteria’s cell wall, preventing it from building up resistance to the antibiotic.
Citing privacy agreements with dirt-donating landowners, Ling declined to provide any details about the origin of the Maine soil sample apart from saying the location was “quite near the coast.”
“This particular bacteria happened to be in the sample that we tested,” said Ling, vice president of research and development at NovoBiotic Pharmaceuticals, the company in Cambridge, Massachusetts, that hopes to develop a drug based on the antibiotic. “There wasn’t anything striking about this particular soil sample or why we went to this particular spot.”
But the results created a buzz in scientific media around the world, both for the discovery of a potentially powerful new drug and for the way that the research team was able to isolate the antibiotic.
Antibiotics are everywhere in the natural world, and are used by microorganisms to help defeat or keep in check other bacteria. Over the past century, humans have been able to turn some of those natural secretions into life-saving medicine, beginning with the mass production of penicillin during World War II.
Up until now, however, researchers have been unable to work with 99 percent of antibiotic-producing microbes in the environment because they do not grow in a laboratory petri dish. But the research team led by Lewis – a co-founder of NovoBiotic – developed a small instrument that essentially tricks these previously “unculturable” microbes into growing inside tiny chambers in the device, known as an iChip, when it is buried in the soil sample.
The scientists estimate they now will have access to 50 percent of the microbes in soils, up from 1 percent, as they try to develop more effective antibiotics.
“This platform gives us access to a lot of unknowns out there,” Ling said. “To me, it is almost like going to the moon or to outer space.”
Infections from drug-resistant bacteria have emerged as a global concern as researchers and pharmaceutical companies struggle to keep pace with pathogens’ ability to make an evolutionary end-run around prescription antibiotics.
The World Health Organization warned last year that the globe may be approaching a “post-antibiotic era – in which common infections and minor injuries can kill.” An estimated 2 million people develop drug-resistant infections – and 23,000 die from them – each year in the United States, according to the U.S. Centers for Disease Control and Prevention.
In 2011, more than 80,000 people in the U.S. developed MRSA, a particularly stubborn type of staph infection once largely contracted in hospitals, but now found in the community. The World Health Organization estimated that people with MRSA infections were 64 percent more likely to die than people who had a non-resistant form.
MRSA also happens to be one of the infections that was vulnerable to the new antibiotic, dubbed “teixobactin,” in preliminary testing on mice. Teixobactin also was effective against a type of drug-resistant tuberculosis that sickened 480,000 people around the world in 2013.
The Maine Center for Disease Control and Prevention reported that there were 130 confirmed cases of “invasive MRSA infections” – the most serious kind, found in parts of the body where bacteria should not be present – in the state in 2013. That is up from 114 the year before and 121 in 2011.
Dr. Jonathan Fanburg at Maine Medical Partners-Pediatrics in South Portland, said it was rare to see MRSA cases in children a decade ago. Fanburg estimates that he now sees two or three drug-resistant infections per month, with MRSA being the most common. The infections manifest themselves as boils in the diaper area and skin abscesses. The most stubborn infections require intravenous antibiotic treatment, which often means hospitalization.
“Drug resistance is a major, progressive, increasing concern for pediatrics,” Fanburg said.
Because of the growing concern about drug resistance, Fanburg and many other doctors are more conservative today about prescribing antibiotics and instead wait to see whether an illness requires drug treatments. But that means some bacterial infections will be more advanced by the time the patient takes antibiotics.
Meanwhile, NovoBiotic Pharmaceuticals continues to test the teixobactin antibiotic harvested from the Maine soil sample. It is unclear if the antibiotic will work as well in humans as it has in mice. Ling said any potential drug that would be developed from the technique is likely six or seven years away.
Teixobactin had not been found in any other soil samples tested, but Ling acknowledged that it might occur elsewhere.
She actually began her work by testing soils in the small backyard of her home in Arlington, Massachusetts. Almost immediately, she discovered a microorganism that was closely related to one thought only to occur in sediments in the Mariana Trench, the deepest part of the Pacific Ocean. To Ling, the finding demonstrates that researchers don’t need to go to extreme places when new discoveries may be underfoot in their literal or figurative backyards – apparently including in “a grassy field in Maine.”
“When you walk on a sand dune, you may think there is nothing there, but you would be amazed by how much you can find,” she said.
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