A 1,000-year-old Anglo-Saxon remedy is giving scientists new ideas for beating antibiotic resistance. The treatment, called Bald’s eyesalve, attacks microbes in multiple ways at once.

The recipe comes from Bald’s Leechbook, a 10th-century medical text held by the British Library. It mixes garlic, onion, bovine bile and wine in a brass vessel, then lets the brew stand for nine days.

In 2015, microbiologist Freya Harrison and colleagues at the University of Nottingham recreated the recipe. In lab tests, it killed up to 90 percent of MRSA, the drug-resistant form of Staphylococcus aureus. It also destroyed sticky bacterial biofilms that antibiotics struggle to penetrate.

New research has now examined how the eyesalve affects pathogens. After treatment, hundreds of bacterial genes were expressed differently. The brew damaged bacterial membranes and reduced their ability to form biofilms. It also blocked the cell communication that bacteria use to coordinate attacks.

For bacterial colonies to survive the mixture, they would have to mutate multiple targets at once. That is far more difficult than resisting a single drug.

Antibiotic-resistant infections kill more than one million people each year. Mixture-based treatments from ancient texts could inspire modern medicine.