The remedy appears in Bald’s Leechbook, a mid-900s medical text from Winchester. It calls for equal parts crushed garlic and either onion or leek, mixed with cow bile (ox gall) and English wine, then stored in a brass or bronze container for exactly nine nights.
In 2015, microbiologists from the University of Nottingham and Texas Tech reproduced the salve under sterile conditions and found it wiped out mature biofilms of methicillin-resistant Staphylococcus aureus (MRSA) on mouse wounds far more effectively than standard antibiotics.(https://britishlibrary.typepad.co.uk/science/2015/04/a-medieval-medical-marvel.html)
Dr Christina Lee, an Anglo-Saxon expert from the University’s School of English, translated the recipe which was made from a mixture of garlic, onions, wine, and bovine bile salts, all of which were then brewed in a brass cauldron and let sit for nine days:
“take cropleek and garlic, of both equal quantities, pound them well together, take wine and bullocks’ gall, of both equal quantities, mix with the 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 it with a feather to the eye.”
The microbiologists made three batches and tested them on cultures of three commonly found and hard to treat bacteria, Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa in both synthetic wounds and in infected wounds in mice. The results were then compared to a control treatment using the same recipe, but without the vegetable compounds. On their own the ingredients had no measureable effect, but when combined the mixture was startling effective: only about one in a thousand bacteria survived application. Vancomycin, the current antibiotic of choice against MRSA, has approximately the same level of antibacterial activity.