He was messy enough to save 200 million lives.

Fleming's Contaminated Plate: The Accident That Saved 200 Million Lives

A Scottish bacteriologist's messy lab revolutionizes medicine

Alexander Fleming's contaminated petri dish in 1928 led to the discovery of penicillin — an accident that ultimately saved over 200 million lives.

Alexander Fleming returned from a holiday in September 1928 to find one of his petri dishes contaminated with mold — a common enough occurrence that most bacteriologists would simply discard the plate. Fleming noticed something unusual: a clear zone surrounded the mold growth, suggesting the mold was producing something that killed bacteria.

The mold was Penicillium notatum. The substance it produced — which Fleming named penicillin — inhibited the growth of Staphylococcus aureus and several other bacteria. Fleming published his results in 1929 and tried to purify the compound, but chemical difficulties and lack of interest from colleagues stalled the work.

For ten years, penicillin remained a curiosity. Then, in 1939, Howard Florey and Ernst Chain at Oxford systematically investigated Fleming's compound. They purified it, tested it on mice, and conducted the first human trial in 1941 — treating a policeman near death from septicemia. He recovered dramatically until the penicillin supply ran out. He died.

Mass production followed as the Allied powers prioritized penicillin manufacture for the war. By D-Day, June 1944, enough penicillin existed to treat all Allied casualties. Wou…

💡 Fleming was famously messy. His lab was described as perpetually cluttered with contaminated dishes. Had he been tidier, he likely would have thrown away the crucial plate.