On 15 September 1928, Scottish scientist Alexander Fleming made one of the most important breakthroughs in medical history: the discovery of penicillin, the world’s first true antibiotic.
Fleming’s life and career
Born in Ayrshire, Scotland, in 1881, Fleming studied medicine at St Mary’s Hospital Medical School in London. He trained as a bacteriologist and served as a captain in the Royal Army Medical Corps during the First World War, where he witnessed first-hand the devastating effects of infected wounds. This experience deepened his determination to find ways of controlling bacterial infections.
After the war, Fleming returned to St Mary’s, where he became a professor of bacteriology. Known for his meticulous yet curious approach, he was respected by colleagues for his sharp observations, though not always for tidy laboratory habits—a trait that inadvertently led to his most famous discovery.
The discovery of penicillin
In September 1928, Fleming noticed something unusual in one of his Petri dishes containing colonies of Staphylococcus aureus, a bacterium responsible for many infections. A spore of mould, later identified as Penicillium notatum, had contaminated the dish. Around the mould, the bacteria had been destroyed, while colonies further away continued to thrive.
Fleming realised that the mould was releasing a substance that killed or inhibited the growth of certain bacteria. He named this substance penicillin. Although Fleming published his findings in 1929, he struggled to purify and stabilise the compound. It was not until the early 1940s that a team at Oxford, led by Howard Florey and Ernst Chain, developed techniques for large-scale production, just in time to treat infected wounds and illnesses during the Second World War.
Impact on modern medicine
The discovery of penicillin revolutionised medicine. For the first time, doctors had a reliable way to treat bacterial infections such as pneumonia, meningitis, syphilis, and bloodstream infections that were once often fatal. Penicillin saved countless soldiers’ lives during the war and went on to transform public health worldwide.
Today, penicillin and its derivatives remain among the most widely used antibiotics, forming the basis for many treatments against bacterial diseases. Despite the growing challenge of antibiotic resistance, Fleming’s breakthrough laid the foundation for modern antimicrobial therapy.
Legacy
For his discovery, Fleming shared the 1945 Nobel Prize in Physiology or Medicine with Florey and Chain. His work not only changed medical practice but also opened the door to a golden age of antibiotic research. Fleming himself warned of the dangers of misuse, predicting that overuse could lead to resistant strains of bacteria—a warning that has proved prescient.
Penicillin is often hailed as the “miracle drug”, and Fleming’s contribution is celebrated as one of the greatest achievements of twentieth-century science. His accidental yet brilliant observation has saved hundreds of millions of lives and continues to shape the fight against infectious disease.
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