When a new antibiotic comes out, it usually doesn’t take long for it to stop working as well as it should. Bacteria, which can replicate in as little as 20 minutes, can sometimes evolve to resist a drug in less than a year (in the lab, you can watch it happen in 10 days). For some diseases–like gonorrhea–there may soon no longer be any antibiotics left that work.
It’s possible that doctors may eventually start using another tactic entirely: tiny star-shaped polymers that can tear bacterial walls apart. In a recent study in Nature Microbiology, researchers reported that their new nano-engineered design can kill drug-resistant bacteria without harming the cells around them.
“I guess it started as a hunch,” says 25-year-old Shu Lam, a PhD student at the University of Melbourne and lead author of the paper. Lam is part of a team that had been working on the new polymer for a few years and realized that the new material might be useful against bacteria. “We sort of modified the design as we went, and it worked out.”
The bacteria don’t seem to be able to evolve to resist the polymers. “We set up a situation in the lab that actually sort of promotes the bacteria to develop resistance against the polymers,” says Lam. The researchers surrounded the bacteria with low doses of the polymer–the same situation that would create resistance to antibiotics. But after around 600 new generations of bacteria, the polymers were still working.
The polymers are designed with a positive charge, so they can attract bacteria, which have a negative charge (healthy human cells have a neutral charge). “They stick to the negatively charged bacteria like a magnet,” she says. The polymers also bind to certain components of the bacteria surface.
While other researchers have attempted to use similar peptides–small chains of amino acids–to kill bacteria in the past, those other attempts also killed off healthy cells. The new design about 10 times larger, which may be why it doesn’t seem to kill red blood cells; the researchers hypothesize that it may be too big to affect them.
It will take a lot more time and testing before researchers can prove that this type of treatment wouldn’t have harmful side effects. In the meantime, the world is beginning to attempt to save current antibiotics–which could continue working much longer if they weren’t misused.
Roughly 80% of antibiotics in the U.S. are used in farm animals, often to keep the animals healthy in cramped factory farms rather than to actually treat disease. An estimated half of the drugs prescribed for humans are given out for things like the flu, which can’t be treated with antibiotics. Every time the drugs are overused, bacteria have more chances to evolve against them.
At a UN meeting on September 21, world leaders agreed that antibiotic resistance is a “fundamental threat” to health and pledged to start doing something about it. By 2050, an estimated 10 million people could die a year from infections that are no longer treatable with antibiotics.
If antibiotics can’t be saved–or can’t be saved for some especially hard to treat diseases–the Australian researchers hope that their polymers will be able to step in before we go back to a pre-antibiotic world, where a scrape and a simple infection might mean death.
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