Discovery of Penicillin began with a messy petri dish in a London lab in 1928. Alexander Fleming spotted blue green mold and a clear ring where bacteria had once grown. In fact, it was during this observation that he discovered the remarkable ability of Penicillium mold to kill surrounding bacteria. He named the antibacterial substance penicillin and published his finding in 1929.
Discovery of Penicillin in a few simple steps
Fleming worked as a Scottish bacteriologist in London. He noticed a plate of Staphylococcus bacteria with a clean halo around Penicillium mold. He wrote about it but could not make large amounts. Then, about a decade later, Howard Florey and Ernst Chain purified and tested penicillin. Their teams at Oxford developed methods that allowed mass production by about 1941. Notably, the first clinical administration of purified penicillin was given on February 12, 1941, to patient Albert Alexander during initial human trials, marking a significant milestone in medical history.
Why the discovery mattered
Discovery of Penicillin changed medicine in dramatic ways. Before antibiotics, minor infections could be fatal. Surgeons and families feared everyday infections. With penicillin, doctors could treat wounds, pneumonia, and post childbirth infections more safely. In 1945, Fleming, Florey, and Chain shared the Nobel Prize in Physiology or Medicine for their work, recognizing the curative effects of penicillin in various infectious diseases. Moreover, during World War II, U.S. wartime production of penicillin scaled dramatically, from 21 billion units in 1943 to over 6.8 trillion units in 1945 to meet urgent needs.
How penicillin works and important notes
Penicillin kills bacteria by stopping their ability to build cell walls. Human cells do not use that same wall building, so they stay safe. Because of this, penicillin became the first widely used antibiotic. The original Fleming Penicillium isolate produced very low penicillin titers (~2 international units [IU]/mL), but strain improvement efforts raised yields substantially to up to ~300 μg/mL for the X-1612 mutant, illustrating the scientific advancements that improved penicillin production.
- Penicillin fights many bacterial infections but not viruses. It will not help colds or flu.
- Some people are allergic to penicillin. Reactions range from mild rashes to serious problems.
- Bacteria can become resistant. Overuse and misuse of antibiotics helped resistance grow.
Also remember, Fleming’s messy dish was only the start. Careful science, purification, mass production, and teamwork made penicillin safe and widely available.
Share a tiny activity and a gentle note
Instead of growing mold, draw Fleming’s messy dish together. Ask your child to label the mold, the clear zone, and a small scientist thinking “Hmm.” This keeps the wonder without the mess. Small, playful moments like this build big curiosity.
Read or listen to a story about Discovery of Penicillin now: Read or listen to a story about Discovery of Penicillin now: For 3-5 year olds, For 6-8 year olds, For 8-10 year olds, and For 10-12 year olds.
I also made a short Storypie listen called “Meet Alexander Fleming.” Try it during snack time to spark curiosity. If you like, visit Storypie to get the app and explore more tiny true stories.
