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The Discovery of Penicillin and its Impact on Modern Medicine

The antibiotic saved many lives during WWII and afterward.

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  • Sir Alexander Fleming in his laboratory in 1943.Photo Credit: Wikipedia

In 1945, Scottish physician and microbiologist Alexander Fleming shared the Nobel Prize in Physiology or Medicine with Howard Florey and Ernst Boris Chain. The reason for their honor? “The discovery of penicillin and its curative effect in various infectious diseases,” according to the Nobel Committee, a discovery that has been hailed as the “single greatest victory ever achieved over disease.”

By the time Fleming was examining the effects of the mold that turned out to be what we now know as Penicillium rubens, however, the antibiotic effect of mold was already well known, if not well understood. Throughout the ancient world, people had used molds of various kinds to inhibit the spread of infections. Records of the use of mold to treat wounds go back to before the 17th century, when wet bread was sometimes mixed with spider webs and plastered over injuries.

In 1871, John Scott Burdon-Sanderson and Joseph Lister, the English surgeon who is considered the father of modern antiseptics, both separately observed that mold could inhibit the growth of bacteria. Other important figures in the history of medicine also worked in this field, including Louis Pasteur, credited with the discovery of both vaccination and pasteurization, the latter of which shares his name.

It was Fleming who coined the term penicillin, however. In 1928, while working at St Mary’s Hospital in London, he left several culture plates inoculated with the S. aureus bacteria on his desk. When he returned, he discovered that one of the plates had been contaminated with a blue-green mold—and in that plate, the bacteria hadn’t grown. 

During his Nobel lecture, while explaining why he called the substance he extracted from the mold “penicillin,” he stated that, “I simply followed perfectly orthodox lines and coined a word which explained that the substance penicillin was derived from a plant of the genus Penicillium just as many years ago the word ‘Digitalin’ was invented for a substance derived from the plant Digitalis.”

At the time, however, he proffered a simpler explanation in his notes, when he stated that he coined the term “to avoid the repetition of the rather cumbersome phrase ‘mould broth filtrate.’”

Though Fleming was the one to name the discovery, he shared the Nobel Prize for a reason. In 1929, Fleming’s discovery was an important footnote, but it was not yet the medical breakthrough that penicillin would become. For that, another team was needed.

In 1939, Ernst Boris Chain found Fleming’s 1929 paper while working at the Sir William Dunn School of Pathology in Oxford. He brought the idea of furthering the research to Howard Florey, who was then in charge of the school, and from there to an interdisciplinary team including Edward Abraham, Mary Ethel Florey, Arthur Duncan Gardner, Norman Heatley, Margaret Jennings, Jean Orr-Ewing, and Gordon Sanders. At the time, according to Chain, “that penicillin could have practical uses in clinical medicine did not enter our minds when we started our work on penicillin.”

And yet, those practical uses are exactly what they found. Their research included developing methods for cultivating the mold that produced penicillin, as well as extracting, purifying, and storing the penicillin itself. The team created an assay for measuring the purity of penicillin and, perhaps most importantly, carried out the clinical trials necessary to prove its efficacy, beginning with animal experiments before moving on to human trials. 

Though the government and private sectors were slow to embrace the possibilities of this new discovery, a change was coming that would help to push penicillin to the forefront of medicine. When World War II broke out, penicillin became part of the Allied war effort, and is credited with saving the lives of thousands of Allied soldiers. Partly through its use in the war, the mass production of penicillin was pioneered throughout the 1940s, and by the time the war ended in 1945, penicillin was widely available. As one of the first commercially produced antibiotics, penicillin saved countless lives and changed the way we treat disease.

Though today we think of penicillin primarily as a medicine, and that was certainly its first intended use, one of the biggest uses for penicillin historically has been in agriculture. During studies conducted in the 1940s and into the 1950s, it was found that adding penicillin to animal feed improved food conversion efficiency and could increase weight gain by as much as 10%. By 1951, the Food and Drug Administration had approved the use of penicillin as a feed additive for poultry and livestock, and farmers became one of the biggest buyers of the drug.

In 1964, Dorothy Hodgkin became the third woman to receive the Nobel Prize in Chemistry for her “determinations by X-ray techniques of the structures of important biochemical substances,” among them penicillin, which she had mapped as far back as 1945. Her determination of the chemical structure of penicillin opened the door for semisynthetic variants that provided more effective antibiotic properties and helped to usher in the mass production of the drug.

However, not everything about the discovery of penicillin was good news. As early as 1940, Ernst Chain and Edward Abraham had already reported the first indications of bacteria that were resistant to penicillin. As the use of antibiotics grew, especially in agricultural settings, the odds of antibiotic resistant strains of bacteria grew with them. 

This stemmed from a variety of causes, including the misuse of antibiotics for the treatment of viruses and other ailments on which they had no effect. A study conducted by bacteriologist Mary Barber in 1946 found that seven out of eight strains of bacteria were susceptible to penicillin, while within two years that number had dropped to three in eight.

Today, antibiotic resistance remains a major health concern all over the world, and it has led many scientists to reconsider not only how we treat disease, but how we apply antibiotics to agriculture and other practices. In the decades since penicillin was first isolated and named, it has been supplemented and even replaced by more effective antibiotics, but its impact on the world’s health—for better, and potentially for worse—cannot be overstated.