Medallion containing original mould from discovery of penicillin goes up for auction

Alexander Fleming is pictured in his laboratory at St. Mary's Hospital in London in 1943. (Davies / Hulton Archive / Getty Images)

A medallion containing some of the original mould involved in the discovery of penicillin is expected to fetch up to US$50,000 when it goes up for auction later this month.

The medallion was created and inscribed by Scottish bacteriologist Alexander Fleming in the course of “one of the most pivotal discoveries in medial history,” auction house Bonhams said in a statement published Wednesday.

The scientist “stumbled across the world’s first antibiotic after accidentally leaving a stack of staph cultures next to an open window while on vacation in 1928,” the statement reads.

“The cultures were contaminated by an airborne mould and before disposing of the cultures, he noticed that the mould had prevented normal growth by the staph,” it adds.

Fleming created the medallion as a gift for his niece and inscribed it with the message: “The mould that made penicillin / Alexander Fleming.”

The medallion contains a specimen of the original penicillin mould on blotting paper, mounted within a glass disc held in place by a black plastic rim 53 millimeters (two inches) in diameter, according to the auction listing.

It is expected to fetch US$30,000-US$50,000 in an online auction that runs from October 13 to 23.

Fleming gave a number of similar medallions to public figures such as Pope Pius XII, Queen Elizabeth II, Prince Philip, Marlene Dietrich, Winston Churchill and Theodore Roosevelt.

“These mould medallions, relics of Fleming’s contribution to humanity, one of the most important advances of the 20th-century, are rare in private hands,” the auction listing reads.

Fleming initially struggled to identify the exact strain of the fungus that created the bacteria-free circle in his petri dish, and over the years, several species of Penicillium have been identified as producing penicillin.

During the 1930s and 1940s, scientists in the United Kingdom and United States evaluated many different strains to see if any could be used to mass-produce penicillin, and the drug saved thousands of wounded soldiers and civilians during World War II.

Penicillin changed the course of modern medicine, with antibiotics key to the decline of many diseases over the course of the 20th century.

Now its effectiveness is threatened by antibiotic resistance.

In his lifetime, Fleming realized that his discovery could be endangered by antibiotic resistance and warned of the dangers in his Nobel lecture in 1945.

“The time may come when penicillin can be bought by anyone in the shops,” he said. “Then there is the danger that the ignorant man may easily underdose himself and, by exposing his microbes to nonlethal quantities of the drug, make them resistant.”

Drug resistance is expected to result in 10 million deaths a year by 2050 as bacteria outsmart our most sophisticated drugs.

CNN’s Katie Hunt contributed to this report.