Medieval Potion Shown to Kill Problematic Bacteria

A new study revisits a 1,000-year-old remedy that is remarkably effective today.

Old English book
The leechbook.

 © The British Library Board (Royal 12 D xvii)

In 2015, a microbiologist and an Anglo Saxon scholar decided to test a recipe from a 10th-century Old English medical compendium called Bald's Leechbook; what they found surprised everyone. The potion, called "Bald's eyesalve," was tested on soft tissue infected with the antibiotic-resistant methicillin-resistant Staphylococcus aureus – otherwise known as the hospital superbug MRSA. It killed 90 percent of the bacteria, the same efficacy as vancomycin, the antibiotic that is used for MRSA.

Now the researchers are at it again, mixing up new batches of the eyesalve – a potent brew of onion, garlic, wine, and bile salts – to test in treating biofilm-associated infections. And once again, what they found is no less exciting.

Looking at natural remedies to fill in the antibiotic discovery gap, the researchers conclude that "medieval methods using natural antimicrobials from every day ingredients could help find new answers," notes the University of Warwick, where the research was done.

As Doctor Freya Harrison, the aforementioned microbiologist explains:

"We have shown that a medieval remedy made from onion, garlic, wine, and bile can kill a range of problematic bacteria grown both planktonically and as biofilms. Because the mixture did not cause much damage to human cells in the lab, or to mice, we could potentially develop a safe and effective antibacterial treatment from the remedy."

While the earlier work focused on MRSA, the new study looked at the two ways that bacteria can live: as individual planktonic cells or as a multicellular biofilm. "Biofilm helps protect bacteria from antibiotics, making them much harder to treat," the University explains. "One such biofilm that is particularly hard to treat is those that infect diabetic foot ulcers."

They found the Bald's eyesalve remedy worked against a range of wound pathogens in planktonic culture. The University notes that the activity is maintained against the following pathogens grown as biofilms:

1. Acinetobacter baumanii – commonly associated with infected wounds in combat troops returning from conflict zones.
2. Stenotrophomonas maltophilia – commonly associated with respiratory infections in humans
3. Staphylococcus aureus – a common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning.
4. Staphylococcus epidermidis – a common cause of infections involving indwelling foreign devices such as a catheter, surgical wound infections, and bacteremia in immunocompromised patients.
5. Streptococcus pyogenes – causes numerous infections in humans including pharyngitis, tonsillitis, scarlet fever, cellulitis, rheumatic fever and post-streptococcal glomerulonephritis.

As it so happens, all of these bacteria can be found in the biofilms that infect diabetic foot ulcers, which can be resistant to antibiotic treatment.

"These debilitating infections can lead to amputation to avoid the risk of the bacteria spreading to the blood to cause lethal bacteremia," says the University.

The "Ancientbiotics" research team was established in 2015 and provides a brilliant window into effective ways to conduct research. By creating an interdisciplinary group of scientists and scholars – including microbiologists, chemists, pharmacists, data analysts, and medievalists at Warwick and in the United States – problem-solving becomes a much more dynamic endeavor.

Like, who would think to invite an Anglo Saxon specialist to a microbiology party?

The actual eyesalve remedy text.
The actual eyesalve remedy text.  The British Library Board (Royal 12 D xvii)

But of course, without the work of Doctor Christina Lee, from the School of English at the University of Nottingham, Bald's Leechbook might have remained more gibberish than groundbreaking. Here is her translation for the "work and eye salve for a wen":

"Take cropleek and garlic, of both equal quantities, pound them well together, take wine and bullocks gall, of both equal quantities, mix with a leek, put this then into a brazen vessel. Let it stand nine days in the brass vessel, wring out through a cloth and clear it well, put it into a horn, and about night time apply with a feather to the eye; the best leechdom.”

As was concluded with the MRSA study, it's not the individual parts that make the magic, but the combination of ingredients. They explain that while the garlic's allicin can work against planktonic cultures, garlic alone has no activity against biofilms, "and therefore the anti-biofilm activity of Bald's eyesalve cannot be attributed to a single ingredient and requires the combination of all ingredients to achieve full activity." And brewed with brass and allowed to stand for nine days, of course.

The Leechbook lives in the British Library and is widely regarded as one of the earliest known medical textbooks. With its Anglo-Saxon medical advice and recipes for medicines, salves, and treatments – who knows what other cures it might contain? As Lee observes, "Bald's eyesalve underlines the significance of medical treatment throughout the ages. It shows that people in Early Medieval England had at least some effective remedies."

The paper, "Anti-biofilm efficacy of a medieval treatment for bacterial infection requires the combination of multiple ingredients," was published in Scientific Reports.