As drug resistance grows, combining antibiotics could turn up new treatments

Combining certain antibiotics could help them pack a one-two punch against harmful bacteria, according to a new study published Wednesday in Nature.

Nassos Typas and his colleagues at the European Molecular Biology Laboratory in Germany tested 3,000 different combinations of antibiotics with each other or with drugs, food additives, and other compounds on three common types of bacteria that infect humans.

“Antibiotic resistance is increasing, and because we haven’t been developing new drugs for the past 20 years, we’re running out,” Typas said. He and his colleagues set out to discover combinations that might be helpful in the clinic — and were on the hunt for patterns that might illustrate why certain pairs work.

They turned up hundreds of combinations that made antibiotic treatment more effective (along with many that didn’t). Pairs of drugs that targeted the same cellular processes were much more likely to be successful than combinations that worked in two different ways.

And many of the interactions were species-specific — that is, a combination might work well together to tackle one type of bacteria, but not another. That finding might one day be beneficial for finding drug combinations that don’t harm the rest of the gut’s microbes.

“If you have a broad-spectrum antibiotic, it doesn’t only eradicate your infection, it also eradicates your gut microbes,” Typas explained. That’s why antibiotics can sometimes come with gastrointestinal side effects. But the effects of the drug combinations are highly selective and, in many cases, only affect a few kinds of bacteria. In the future, it might be possible for researchers to find drug combinations that attack harmful pathogens while preventing any damage to healthy bacteria.

“You could find the drug that works as an antidote for the commensal microbes, but not as an antidote for the pathogens,” Typas said.

In theory, that could also curb the development of antibiotic resistance, Typas said, since healthy bacteria might not have to evolve antibiotic resistance, which can be transferred to harmful pathogens.

The researchers also found that several of the combinations were effective at treating bacteria that’s resistant to several other antibiotics, both in cell models and in studies on moths. They’re now testing some of the combinations in mice.