Scientists discover potentially powerful antibiotic

Liz Szabo | USA TODAY

Scientists have discovered a potentially powerful antibiotic that can kill some of the most dangerous "superbugs" -- serious infections that are resistant to standard medications.

Superbugs, which can't be killed by antibiotics, are a growing threat to public health, according to the Centers for Disease Control and Prevention, sickening 2 million Americans a year and killing 23,000. Researchers have warned that the world is at risk of entering a "post-antibiotic" era in which patients could die from formerly treatable infections and even routine surgeries could become dangerous.

Developing new antibiotics has been a challenge, partly for financial reasons. Finding and testing antibiotics can take a decade and more than $1 billion. Many pharmaceutical companies have shied away from this research because of the huge cost and financial risk.

Finding new antibiotics has also been scientifically difficult.

Bacteria found in things like bread mold make their own antibiotics, which they use as chemical weapons to kill rival germs. For 70 years, researchers have used this microscopic arms race to fight infections in humans.

Although dirt is filled with germs, scientists until now haven't been able to grow these bacteria in a laboratory – a key requirement for studying and testing them. Scientists were able to coax only about 1% of soil bacteria to grow in a lab dish.

Now, scientists led by Northeastern University in Boston have invented a "contraption" to grow germs that could allow them to study about half of soil bacteria, vastly increasing the pool of drug candidates, according to researcher Kim Lewis, coauthor of a study published in Nature.

Lewis and colleagues used a device they call the iChip, which sorts individual bacterial cells harvested from soil into tiny chambers. Scientists then bury the iChip back in the ground, where molecules from the soil seep into the chamber, giving the bacteria the sort of environment in which it naturally likes to reproduce.

The transplanted bacteria "are essentially tricked. They don't know anything has happened to them," says Lewis, a professor at Northeastern. Once the bacteria have begun growing in the iChip, they seem to have no trouble continuing to reproduce in a lab dish, he says.

Researchers tested 10,000 compounds and found 25 new antibiotics, although only one – which they call teixobactin – stands out, says Lewis, who is working with a biotech company called NovaBiotic Pharmaceuticals, located in Cambridge, Mass.

That's because teixobactin killed a dangerous bug called MRSA, or methicillin-resistant Staphylococcus aureus, in mice. Teixobactin also killed a type of drug-resistant tuberculosis. But teixobactin was unable to kill one of the worst of all superbugs -- a deadly infection called Klebsiella pneumoniae, which has evolved to resist all known antibiotics.

Significantly, Lewis and his team found no sign that bacteria were evolving resistance to teixobactin.

Because of the particular way teixobactin kills bacteria, germs won't easily be able to evolve ways around it, says Gerard Wright, a professor of biochemistry at Canada's McMaster University in Hamilton, Ontario. It took four decades for bacteria to become resistant to similar antibiotics, says Wright, who was not involved in the new study but wrote an accompanying editorial.

Researchers have tested teixobactin only in mice. Human trials are still two years away, Lewis says. Completing those human trials will take three years. Most drugs that appear promising in animals fail to pass human tests. Teixobactin produced no serious side effects in mice, but doctors don't yet know if it will be safe enough for people. So even if human tests are successful, teixobactin won't be on the market for at least five years.

But scientists are excited about the possibility of adding new antibiotics to medicine's arsenal.

"In a field dominated by doom and gloom," Wright wrote, the new study "offers hope that innovation and creativity can combine to solve the antibiotics crisis."