Penicillin was accidentally discovered by Alexander Fleming in 1928 while he was investigating the bacteria Staphylococcus. He observed that the presence of mould could kill or prevent the bacteria from reproducing any further. The fortunate breakthrough was a historical turning point in medicine, paving the way for the widespread use of modern antibiotics.
In this article, we’ll explore the origins of penicillin in more detail and explain how this potentially life-saving antibiotic is manufactured.
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The origins of penicillin
Discovered nearly 100 years ago, penicillin is the world’s first true antibiotic. Even today, it’s widely used to treat tonsillitis, meningitis, syphilis, and other bacterial infections.
But exactly how does it work? Penicillin effectively inhibits bacterial reproduction in two ways:
- Firstly, by disrupting the production of enzymes necessary for building bacterial cell walls
- Secondly, by activating other enzymes that destroy the bacterial cell walls
Before antibiotics
Long before antibiotics were discovered, physicians treated wounds and infections with naturally occurring chemicals. However, the topical application of these substances could also damage the surrounding tissue, while others were toxic if taken internally.
For example, in post-medieval Europe, mercury fumigation was used to treat syphilis. As we now know, mercury is very toxic and can cause a host of neurological problems.
During the American Civil War, chemicals such as topical iodine and bromine were widely used to treat minor battle wounds. However, with antibiotics still not invented at this point, many wounded soldiers had their limbs amputated to prevent the spread of infection.
High juvenile mortality
Before the discovery of antibiotics, mortality rates were exceptionally high for those diagnosed with infections. Juvenile deaths due to meningitis were as high as 90%, and the few who did survive suffered severe and lifelong disabilities including deafness and mental health problems.
Thousands of children also died because of conditions like pneumonia and tuberculosis. Even a simple sore throat could be fatal if the infection spread to the brain. Infant mortality was high too, with around 1 in 20 babies dying before their first birthday. Thankfully, the widespread use of antibiotics means this figure has improved substantially and is now just 3.5 per 1,000 live births.
Discovery of penicillin
The discovery of penicillin was a fortunate accident that only occurred because some petri dishes weren’t cleaned properly. In 1928, the Scottish scientist Alexander Fleming, who was employed in a laboratory at St. Mary’s Hospital in London, returned from his holiday to find the petri dishes he’d previously prepared for bacterial growth were contaminated with mould.
He observed that the presence of this mould either killed or prevented the petri dish colonies of Staphylococcus aureus bacteria from reproducing. Upon further investigation, Fleming discovered the moulds were secreting a self-defence substance that was dissolving the cell walls of the microbes. He named this antibacterial substance penicillin after the Penicillium mould that produced it.
Who invented penicillin?
As we’ve explained, Alexander Fleming inadvertently discovered penicillin in 1928 after a batch of petri dish bacterial cultures were contaminated with mould. He later identified and named the substance secreted by the mould, Penicillium notatum.
Fleming performed several experiments to extract and purify the penicillin extracts. He published his findings in the British Journal of Experimental Pathology in 1929, but at the time it failed to attract the attention of other scientists in the field.
It took almost a decade before Fleming’s paper gained traction and other scientists realised they were able to repeat and confirm the results of his experiments.
In 1938, the biochemist Ernst Chain and the pathologist Howard Florey became aware of Fleming’s findings while they were researching antibacterial compounds. The two scientists were able to isolate penicillin from mould secretions and then inject it into mice to test the efficacy of penicillin in treating bacterial infections. They proceeded to test it on humans with great success, which then led to the pharmaceutical drug entering mass production in the 1940s.
Among the numerous awards for his monumental scientific discovery, Fleming – along with Chain and Florey – earned a Nobel Prize for Medicine in 1945.
One sometimes finds what one is not looking for. When I woke up just after dawn on September 28, 1928, I certainly didn’t plan to revolutionise all medicine by discovering the world’s first antibiotic, or bacteria killer. But I suppose that was exactly what I did. — Alexander Fleming
How penicillin is manufactured
Today, penicillin is manufactured from Penicillium mould in large fermentation tanks, typically by pharmaceutical or chemical manufacturing companies. The mould ferments sugar and other ingredients, naturally producing penicillin as a byproduct. The penicillin is then isolated and purified from the fermentation tanks.
Chemical structure of penicillin
A penicillin molecule is composed of a beta-lactam ring, a thiazolidine ring, and a side chain. The side chain is 6-aminopenicillanic acid. Despite the complex molecular structure of penicillin, its antibacterial actions are performed by the beta-lactam ring.
The mass production of penicillin
Penicillin started being mass-produced during World War II, with about 400 million units of the antibiotic manufactured between January and May 1942.
British scientists Howard Florey and Norman Heatley worked with their American counterparts to develop an efficient means of mass-producing penicillin. Instead of using Penicillium notatum, which produced low yields of penicillin, they opted for an alternative mould species known as Penicillium chrysogeum.
They discovered Penicillium chrysogeum was capable of producing 200 times more penicillin than Penicillium notatum. The production of the species was further enhanced using X-rays to mutate the genes and filtration to purify the yields. In the end, the method developed by the scientists produced 1,000 times more penicillin than the original species used by Fleming, ushering in a new era of mass-produced antibiotics.
Conclusion
The Scottish physician-scientist Alexander Fleming accidentally discovered penicillin in 1928 after observing the antibacterial effects of mould on staphylococcus bacteria. However, it took almost a decade before the significance of his research was truly appreciated. Following Fleming’s discovery, the scientists Ernst Chain and Howard Florey were able to isolate penicillin from mould secretions and inject it into humans. The discovery of penicillin changed the course of modern medicine and has prevented countless deaths.
