Scientists create superbug killer

Geoffrey Mohan
Los Angeles Times

Using soil from a grassy field in Maine and a miniaturized diffusion chamber, scientists have cultivated a microbe that could help tame the spread of antibiotic-resistant superbugs.

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 that 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 this week 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 favor of bacteria.

The World Health Organization has warned that the rise of antibiotic-resistant bacteria threatens to undermine the advances made by modern medicine. In the United States, more than 2 million people are sickened by such infections each year, and 23,000 of them die as a result.

Most of the workhorse drugs in use today were developed at least 50 years ago. During the heyday of antibiotic research immediately after World War II, 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 that the molecule, which they called teixobactin, rapidly cleared infections of drug-resistant strains of Mycobacterium tuberculosis and Staphylococcus aureus bacteria, according to the study.