By Vejas Gabriel Liulevicius, Ph.D., University of Tennessee
Penicillin completely revolutionized the treatment of infectious diseases and saved millions of lives. But what is the story behind the discovery of penicillin? And who was Dr. Alexander Fleming, the man responsible for this discovery? Let’s find out more about both the discovery and the discoverer.
Alexander Fleming’s Early Life and Entry into the Medical Profession
Dr. Alexander Fleming was born in rural southwestern Scotland in 1881, into a large family, the seventh of eight children. Like Charles Darwin, Fleming’s youth was spent close to nature, observing and exploring. This shaped his later life and career.
When Fleming was 14, he was sent to London to school. For a while he was employed at a shipping business, but that only made clear to him that he did not want to spend the rest of his life in a commercial career. Eventually, he followed an older brother into the medical profession.
From 1901, Fleming studied at St. Mary’s medical school in London, and he later went on to spend the rest of his career there at St. Mary’s. He studied under the notable bacteriologist Almroth Wright, the discoverer of the typhoid vaccine.
Once Fleming earned his degree, he went into private practice, treating syphilis with Salvarsan which German physician Paul Ehrlich had invented. During the First World War, Fleming worked in a military hospital in France, at a time when many lives were being lost to soldiers being wounded in the trenches and then becoming infected as they were evacuated to the rear.
Fleming experimented with different antiseptic procedures in the military hospital, and found strong chemical antiseptics actually often did more harm than good because they destroyed tissue. After the war he returned to St. Mary’s and continued working on these antiseptic questions.
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The Accident That Led to the Discovery of Penicillin
In 1921, Fleming made an accidental discovery that Antonie van Leeuwenhoek would have much appreciated, and which really made clear how good he was at using accidents.
While experimenting with bacteria, Fleming, who at the time had a bad cold, saw that mucus from his nose fell into a petri dish. Instead of cleaning it, he left it there to see what would happen. Fleming discovered that the bacteria had been disrupted, and this revealed to him the existence of lysosome, a natural human antibacterial enzyme that’s found in body fluids, including tears.
At this point, Fleming was already an established and noted scholar, a successful scientist. His laboratory was marked by creative disorder, rather than severe, efficient regimentation.
The entire building in which Fleming’s laboratory was housed was not in the best of shape, either. In his lab, it was hard to open a window to get any air circulation, so Fleming kept the door open, which connected with the rest of the building.
This turned out to be fateful, because downstairs was a mycology lab, where experiments on fungus and molds were being done at the same time. It was from down there that spores of mold had drifted silently up and into Fleming’s laboratory.
While Fleming was away for his late summer vacation, the weather turned unseasonably warm for London, and this allowed the mold spores to reproduce where they had landed.
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This is a transcript from the video series Turning Points in Modern History. Watch it now, Wondrium.
The Discovery of Penicillin
In early September, 1928, Fleming had just returned from vacation, and was cleaning up his laboratory to prepare for a new season of research. Before going on his holiday in late summer, he had been working with experiments with staphylococci bacteria in small petri dishes.
On September 3, he started to clean up, placing a stack of contaminated dishes into antiseptic trays with antiseptic fluid. But some dishes were out of the reach of the antiseptic. In other words, this project was a mess—contaminated, unclean, with fuzzy growths, something that really was in dire need of cleaning up.
Ordinarily, a laboratory assistant would have set to work, scrubbing and cleaning and getting everything ready for a fresh start.
Instead, Fleming took his time and looked closely, because to his trained eye, something unexpected and interesting was to be seen. He saw in one of the top dishes the greenish-yellow color of mold, and surrounding it, a kind of open area. The mold was somehow inhibiting the growth of the bacteria.
As Fleming investigated further, he discovered that the mold that had insinuated itself into his experiment was Penicillium notatum, a mold that under the microscope looks brush-like, hence its Latin name, Penicillium or ‘small brush’.
What was happening around the mold was that the cells of the bacteria were breaking down—something the mold was producing was working to destroy bacteria. This powerful substance Fleming dubbed penicillin. The antibiotic revolution was launched, giving mankind new tools in an eternal battle against disease.
This scene illustrated the power of serendipity, finding something while looking for something else. Yet, it was not just chance that was at work here. Fortune favors those who are prepared, and in the case of Fleming, those who are attentive enough to take the time to look and observe.
Fleming later declared, with becoming modesty: “Do not wait for fortune to smile on you; prepare yourself with knowledge.” Overall, he was understated about what he had done, saying, “My only merit is that I did not neglect the observation”.
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Developments After the Discovery of Penicillin
Every discovery takes place in a larger context. Fleming’s insight needed to be made practically accessible and useful before it became the turning point that saved millions of lives and transformed medicine into our own times.
After Fleming’s discovery, the question arose of how to use this discovery, how to develop it as a healing tool practically and in cost-effective ways. For a time Fleming continued to experiment with this new product. He isolated it and diluted it, and was glad to find that even in tiny quantities it was really remarkably effective in stopping bacteria.
Fleming tried it out on mice and rabbits, without ill effects, and that was good news too. When he first discovered this strange substance, he called it mold broth or mold juice. Those were pretty good literal descriptions of what it was, but not as scientifically impressive as the new name that he found for it: penicillin. Then, in 1932, Fleming largely gave up active work on it.
Why? Fleming had made this individual discovery, but producing penicillin on a purified and substantial scale was not what his laboratory was designed for. His own interests in fact also tended much more towards noting new research findings, precisely what he’d done in this case, rather than finding practical uses.
Common Questions about Alexander Fleming and Penicillin
After returning to his laboratory after a vacation, Dr. Alexander Fleming noticed something interesting in the petri dishes in the lab. His trained eye recognized that mold was somehow inhibiting the growth of the bacteria. What was happening around the mold was that the cells of the bacteria were breaking down, because something the mold was producing was working to destroy bacteria. This is how Fleming accidentally discovered penicillin.
Penicillin was discovered by Dr. Alexander Fleming in September 1928.
Alexander Fleming discovered penicillin, which triggered the antibiotic revolution and saved millions of lives.
In 1921, while experimenting with bacteria, Alexander Fleming, who at the time was suffering from a bad cold, noticed that mucus from his nose fell into a petri dish. Instead of cleaning it, he left it there to see what would happen. Fleming discovered that the bacteria had been disrupted, and this revealed to him the existence of lysosome, a natural human antibacterial enzyme that’s found in body fluids, including tears.
