A world without antibiotics
Before the 1940s, a small cut, a sore throat or an ear infection could become deadly. Doctors had no reliable medicine to kill bacteria. Pneumonia, scarlet fever and infected wounds killed many people, including children. Penicillin changed that.
An accidental discovery
In 1928, Scottish scientist Alexander Fleming was studying bacteria called Staphylococcus at St. Mary’s Hospital in London. Before leaving on vacation, he stacked some of his culture dishes on a bench.
When he returned in September, he noticed something odd. One dish had become contaminated with a blue-green mould. Around the mould, the bacteria had died, leaving a clear ring.
Fleming identified the mould as Penicillium and called the substance it produced "penicillin." He found it killed many kinds of harmful bacteria.
Fleming later said, "One sometimes finds what one is not looking for."
From discovery to medicine
Fleming couldn’t produce enough penicillin to use as medicine. For about ten years, little happened.
| Year | Event |
|---|---|
| 1928 | Fleming discovers penicillin |
| 1939–1940 | Howard Florey (from Australia) and Ernst Chain (a German-born refugee), with Norman Heatley at Oxford, purify penicillin and show it cures infections in mice |
| 1941 | First human patient, police officer Albert Alexander, improves dramatically but dies when the supply runs out |
| 1941–1943 | Scientists in the U.S. find ways to mass-produce penicillin, using deep fermentation tanks and a high-yield mould found on a cantaloupe in Peoria, Illinois |
| 1944 | Enough penicillin to treat wounded Allied soldiers on D-Day |
| 1945 | Fleming, Florey and Chain share the Nobel Prize in Physiology or Medicine |
Canada also helped: Connaught Laboratories in Toronto and Ayerst in Montreal produced penicillin for the war effort.
How penicillin works
Bacteria are surrounded by a cell wall that keeps them from bursting. Penicillin stops bacteria from building their cell walls properly. As the bacteria grow, their walls weaken and they burst.
Human cells don’t have cell walls, so penicillin doesn’t harm them. That’s what makes it a safe medicine for most people.
Penicillin and other antibiotics do not work on viruses, like those that cause colds and flu, because viruses don’t have cell walls.
Impact
| Before antibiotics | After antibiotics |
|---|---|
| Infections were a leading cause of death | Many infections became easily curable |
| Surgery carried high risk of deadly infection | Surgery, organ transplants and cancer treatments became much safer |
| Wounded soldiers often died of infection | Battlefield survival improved dramatically |
| Childbirth infections were common | Mothers’ deaths dropped sharply |
Penicillin has saved an estimated 200 million lives or more. It began the antibiotic era, and scientists went on to discover many more antibiotics, like streptomycin, which treated tuberculosis.
Penicillin allergy
Some people are allergic to penicillin. Reactions range from a rash to, rarely, a life-threatening reaction. Doctors always ask about allergies before prescribing it. Interestingly, many people who think they’re allergic actually aren’t, and tests can check.
Antibiotic resistance
Fleming warned about a problem in his Nobel lecture: if antibiotics are misused, bacteria can become resistant.
Antibiotic resistance happens through natural selection:
- An antibiotic kills most bacteria.
- A few happen to have genes that let them survive.
- The survivors multiply.
- Soon, the antibiotic no longer works against that strain.
Resistant "superbugs" like MRSA are a growing health threat. To slow resistance:
- take antibiotics only when prescribed by a doctor
- take the full course exactly as directed
- never use antibiotics for viruses like colds
- don’t share or save leftover antibiotics
- wash hands and keep vaccinations up to date to prevent infections
Common mistakes
- Thinking Fleming made penicillin into a medicine by himself. Florey, Chain and others made it usable.
- Thinking antibiotics cure colds.
- Thinking people become resistant to antibiotics. It’s the bacteria that become resistant.
Try it yourself
- Leave a slice of bread or an orange in a sealed bag for a week. Look for blue-green mould (don’t open the bag).
- Draw a comic showing Fleming’s discovery step by step.
- Use coloured beads to model how antibiotic resistance spreads in a population of bacteria.
Quick recap
- Alexander Fleming discovered penicillin from Penicillium mould in 1928.
- Florey, Chain and Heatley turned it into a usable medicine around 1940.
- Penicillin kills bacteria by breaking down their cell walls.
- It saved millions of lives and started the antibiotic era.
- Misusing antibiotics causes resistance, a serious modern health threat.