Microbe in dirt could kill deadly superbugs
Scientists in the US have cultivated a microbe which can kill germs like MRSA so quickly they don't have time to develop resistance
PUBLISHED : Friday, 09 January, 2015, 3:05am
UPDATED : Friday, 09 January, 2015, 3:05am
Tribune News Service
Microbe in dirt could kill deadly superbugs
Using soil from a grassy field in Maine, scientists have cultivated a microbe that could help tame the spread of antibiotic-resistant superbugs by killing germs so quickly they do not have time to evolve resistance.
When tricked into growing in a lab, the microbe makes a compound that kills strains of tuberculosis, MRSA and other deadly pathogens that are immune to even the most powerful drugs. Tests in mice showed the newfound molecule is "exquisitely active against some very hard-to-deal-with bugs," said Northeastern University microbiologist Kim Lewis, the senior author of a study published in the journal Nature.
Experts said the discovery could lead to a new class of antibiotics for the first time in decades. If so, it would give doctors a much-needed weapon in the microbial arms race that has tilted in favour of bacteria.
The World Health Organisation has warned that the rise of antibiotic-resistant bacteria threatens to undermine the advances made by modern medicine.
Most of the workhorse drugs in use today were developed at least 50 years ago. During the heyday of antibiotic research immediately after the second world war, soil microbes yielded the mainstays in the fight against deadly infections.
Lewis and his colleagues revived that idea to find a new species of bacteria they named Eleftheria terrae.
Soil is chock full of microbes, but most don't readily form colonies in petri dishes. In addition, many of the organisms uncovered in such samples are identical or similar to ones already developed.
"You inevitably are rediscovering penicillin and streptomycin," Lewis said.
To encourage new bacteria to grow, the researchers couldn't just dump their dirt into a laboratory dish. Instead, they isolated minuscule samples in diffusion chambers that functioned as bacterial incubators. Then they put the samples back in the soil.
"Essentially we're tricking the bacteria," Lewis said. "They start growing and form colonies."
The experiment yielded about 10,000 strains of bacteria, which were laboriously sorted and studied.
Researchers then checked to see whether any of the strains could kill streptococcus bacteria.
Finally, they extracted the antibacterial molecule from E. terrae, one of the more promising strep killers. Trials on mice showed the molecule, which they called teixobactin, rapidly cleared infections of drug-resistant strains of Mycobacterium tuberculosis and Staphylococcus aureus bacteria, according to the study. They also felled two kinds of bacteria that cause serious infections of heart tissue, Lewis said.
The compound attacks these and other gram-positive bacteria by binding to chemicals essential to forming cell walls, causing them to break down.
"Not only one target is attacked, but multiple targets, and they are all lethal," said study coauthor Tanja Schneider of the University of Bonn in Germany.
This mechanism of destruction makes it much more difficult for bacteria to develop resistance to teixobactin. Most antibiotics attack proteins, but the DNA that codes for these proteins is known to mutate. Over time, some of these mutations allow bacteria to evade a drug's lethal effects.
The DNA that includes instructions for making cell walls is far less likely to mutate, researchers said. Indeed, when they tried to encourage bacteria to develop resistance to teixobactin, they couldn't.
Lewis said teixobactin kills so quickly that target bacteria will have less time in which to develop resistance.
It took about 30 years for bacteria to develop resistance to a similarly acting antibiotic, the study noted. Researchers said any new drug probably would remain effective at least as long.
Converting teixobactin into a safe and marketable drug could take about five years and cost several hundred million dollars, while clinical trials could be two years away according to the academic-biotech coalition that made the discovery.
