This Medieval Potion Kills Stubborn Bacteria

“Bald’s eyesalve” is effective against numerous strains of bacteria—and could help treat diabetic foot and leg ulcers

Bald's leechbook
Bald's Leechbook, a tenth-century medical text that contains Anglo-Saxon medical advice and recipes for medicines, salves and treatments © The British Library Board

Suffering from an eye infection? A medieval medical text suggests treating it with “Bald’s eyesalve,” a mixture of garlic, onion, wine and just a smidgen of cow bile. Now, more than a millennium after its development, new research has proven that this unusual remedy actually works.

The findings, published last week in the journal Scientific Reports, also indicate that the brew may be effective at combating bacteria strains that are resistant to traditional antibiotics.

Per the study, Bald’s eyesalve appears to shows promise against biofilm infections, or groups of bacteria that have banded together to create a protective barrier, making them particularly challenging to kill. Fighting these types of infections often requires an antibiotic concentration 100 to 1,000 times higher than needed to eradicate the same biofilm-free bacteria.

The growing menace of drug-resistant bacteria inspired the paper’s authors to peer back in time in hopes of identifying novel weapons in the fight against these so-called superbugs.

“Plants have been used as medicines against infection for millennia, and we’ve only scratched the surface in understanding their true potential,” Cassandra Quave, an ethnobotanist at Emory University who wasn’t involved in the new research, tells Gizmodo’s George Dvorsky.

Bald’s eyesalve—detailed in an early tenth-century text called Bald’s Leechbookfirst piqued the interest of co-author Freya Harrison, a microbiologist at the University of Warwick, in 2015.

“When you read it as a microbiologist, you think that it’s got to do something because every ingredient in it has some antibacterial activity when you test it in a test tube. It seemed like a sensible one to put together,” Harrison tells Katie Hunt of CNN. “It’s also very clearly targeted to a bacterial infection from the description of the symptoms in the book.”

Vials of the recreated salve
Vials of the recreated salve University of Warwick

The researchers’ earlier work demonstrated that the 1,000-year-old concoction showed promise in the lab, killing the bacteria responsible for staph infections and MRSA (an antibiotic-resistant type of staph). The new paper expands on this research, highlighting potential applications in an attempt to turn the find into “something clinically useful,” says Harrison.

To test the salve, the scientists mixed dozens of batches and applied them to bacteria colonies known to infect wounds. Some colonies were free-floating, or planktonic, while others had protective biofilms.

Harrison and her colleagues found that the medieval recipe was effective against a range of bacteria, including five biofilms commonly linked to diabetic foot ulcers, according to a statement. Crucially, the mixture didn’t appear to be particularly harmful to either human or mouse cells.

Speaking with CNN, Harrison notes that the research shows “particular promise” in treating diabetic foot infections, which she describes as “the ultimate, super-resistant biofilm infection.”

The microbiologist adds, “There’s a high risk that these diabetic foot ulcers are completely resistant to any antibiotic treatment. Then there’s a risk of a person developing sepsis ... and people end up having their foot or lower leg amputated.”

Interestingly, the salve didn’t contain just one ingredient that could be isolated and used on its own. Instead, the solution required all of its ingredients to work effectively.

“This study is exciting because it demonstrates how mixtures of specific plant ingredients, such as those found in Bald’s eyesalve, can sometimes work better than individual components in fighting infection,” Quave tells Gizmodo.

In the statement, Harrison explains that most antibiotics in use today were derived from natural compounds. She points out that the team’s research “highlights the need to explore not only single compounds but mixtures of natural products for treating biofilm infections.”

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