An antibiotic discovered about 80 years ago, once abandoned and nearly forgotten, might now offer a powerful solution to fighting drug-resistant “superbugs.” These superbugs are bacteria that have evolved to resist many of the drugs we rely on today.
Today, about half of the antibiotics in use are variations of drugs developed nearly a century ago during the “golden age” of antibiotics. One such antibiotic, called streptothricin, was first discovered in the 1940s. Researchers found it to be particularly effective against a type of bacteria called gram-negative bacteria.
Gram-negative bacteria are especially tough to fight because, unlike gram-positive bacteria, they lack the thick cell wall many antibiotics target. This makes them harder to treat, and as a result, finding drugs to combat them has been a huge challenge for scientists.
In 2017, the World Health Organization (WHO) identified gram-negative bacteria as some of the most dangerous drug-resistant pathogens. Despite its effectiveness against bacteria, streptothricin was dismissed early on because studies found it too toxic for human kidneys. It was shelved and rarely revisited in scientific research.
But now, Dr. James Kirby and his team from Harvard University have decided to take another look at streptothricin. They’ve renamed it nourseothricin and are testing its potential as a treatment for modern drug-resistant bacteria. “With the rise of pathogens resistant to multiple drugs and a lack of effective treatments, it’s time to re-examine these overlooked antibiotics,” Kirby explained.
What Is Nourseothricin?
Nourseothricin, a natural product made by gram-positive soil bacteria, is actually a mix of different antibiotics. Each one has a specific name, like streptothricin F (S-F) and streptothricin D (S-D). Lab studies show that while some forms of nourseothricin, such as S-D, are indeed toxic to kidney cells, S-F appears safe for kidneys yet still powerful against gram-negative bacteria.
Tests on mice demonstrated that S-F could kill drug-resistant bacteria without causing significant toxicity, even for strains of bacteria that resist other drugs. This discovery is promising for developing new treatments against superbugs, which have been hard to combat with existing antibiotics.
Soil Bacteria’s Secret Weapon
Soil-dwelling bacteria have had millions of years to develop defenses against other bacteria, which includes producing antibiotics that can penetrate gram-negative bacteria. Streptothricins are a result of this evolutionary battle, helping bacteria in soil survive competition with other microbes. According to Kirby, these compounds could offer a way to break down the defenses of gram-negative bacteria.
Although scientists still don’t fully understand how streptothricin works, early studies suggest that it binds to gram-negative bacteria and disrupts their protein-building process in a unique way. If researchers can decode this mechanism, it could open the door to creating a completely new class of drugs targeting superbugs that resist most other treatments.
Future Steps for Streptothricin Research
Dr. Kirby and his team are already working to enhance S-F, aiming to make it even more effective in killing drug-resistant bacteria. “We’re hopeful that there will be renewed interest in this significant, yet largely forgotten, class of antibiotics,” Kirby said. Researchers are optimistic that streptothricin could inspire the development of new, life-saving antibiotics in the fight against drug-resistant pathogens.
The study was published in PLOS Biology.
