A big day in history: Alexander Fleming discovers penicillin

Dominic Sandbrook nominates 28 September 1928 – the date that Alexander Fleming apparently discovered penicillin – as a big day in history...

British microbiologist and discoverer of penicillin, Alexander Fleming. (Photo by Ipsumpix/Corbis via Getty Images)

“When I woke up just before dawn on 28 September 1928, I certainly didn’t plan to revolutionise all medicine by discovering the world’s first antibiotic, or bacteria killer,” remarked Alexander Fleming, years afterwards. “But I suppose that was exactly what I did.”


The story of Fleming’s ‘discovery’ of penicillin, the ground-breaking antibiotic that saved so many lives, remains one of the most inspiring in scientific history. A brilliant experimental chemist at St Mary’s Hospital in London, the stocky Scotsman had just returned from holiday with his family. Before leaving, he had been studying staphylococcus, the germ that causes septic infections. Incurably untidy, Fleming had left a great pile of germ cultures heaped in a corner of the laboratory. Now, on his return, he noticed that one of the Petri dishes had become contaminated with a kind of blue-green mould. Around the mould, the dish was clear of bacteria, almost as if the mould itself had killed it. Puzzled, Fleming showed the dish to his assistant Merlin Pryce. They discovered that the mould was a strain of penicillium, which Fleming assumed had got in through an open window.

And that, the legend goes, was that. Fleming had his wonder drug; the world had its antibiotic. But the real story is rather more complicated.

In fact, when Fleming set his graduate students to work on the mould, hoping that its ‘juice’ would prove a natural and harmless antiseptic, the early results were disappointing. The juice worked painfully slowly, while Fleming found it hard to keep the concentration sufficiently high around infected areas. The wonder drug, it seemed, was not so wonderful. And when he published his findings in the British Journal of Experimental Pathology in the summer of 1929, the reception was less than ecstatic. Fleming discussed penicillin’s potential as a natural antiseptic to kill septic and pneumonia germs, but he made no great claims for its role as a general antibiotic. His big day in September, it appeared, had not been quite so big after all.

In the decade that followed, Fleming lost interest in penicillin. It would not last long enough in the human body, he concluded, to make a major difference. But in 1938 an Australian chemist working at Oxford, Howard Florey, together with Ernst Chain, a Jewish refugee from Hitler’s Germany, began to look into Fleming’s work. With the assistance of Dorothy Hodgkin, a pioneering female chemist, they worked out the chemical structure of penicillin, devised a way of mass-producing it, and carried out the first successful clinical trials. When Fleming read about their experiments, he telephoned Florey and announced that he was coming to Oxford to see their results. “Good God!” said Chain. “I thought he was dead.”

At first, Fleming seemed delighted with the Oxford group’s application of ‘his juice’. But as time went by and the British and American governments, conscious of penicillin’s potential, started encouraging mass production, rivalry began to grow. In August 1942, the Oxford scientists gave Fleming enough penicillin to treat one of his brother’s employees, who was suffering with septicaemia. But a month later, a controversy broke out in the letters pages of The Times, with St Mary’s and Oxford chemists openly bickering about the real ‘inventor’ of penicillin. Journalists flocked to both laboratories and found Fleming’s story by far the more compelling, the romantic tale of a lone scientist, this shy scholarship boy from rural Ayrshire who through hard work, inspiration and sheer good luck had discovered a drug that changed human history. From that point onwards, the legend of September 1928 was set in stone.

The impact of antibiotics in recent history is almost impossible to overstate; it is surely no exaggeration to say that without them, tens of millions of people would have died young. The tale of 28 September gave this story a satisfyingly iconic hero and turned it into a parable about the role of serendipity in scientific discovery. Yet, to his credit, Fleming himself knew that it was a legend, even calling it the ‘Fleming myth’. Scientific breakthroughs are rarely the work of one man working in isolation; true eureka moments are almost unknown. “Developing penicillin was a team effort, as these things tend to be,” Howard Florey said later. But the events of 28 September 1928 make a better story – and that, of course, is why they will never be forgotten.

Dominic Sandbrook’s latest book is State of Emergency: The Way We Were: Britain, 1970–1974 (Allen Lane). He is a frequent guest on Radio 4’s Saturday Review.


This article was first published in the October 2011 issue of BBC History Magazine