The Mould in the Dirty Dish

Alexander Fleming was, by the cheerful admission of everyone who knew him, not a tidy man. In September 1928 he returned to his cramped laboratory at St Mary's Hospital, London, from a two-week family holiday, and began sorting through the stacks of culture plates he had left unwashed on the bench. On one — a plate of staphylococcus bacteria — a blob of mould had grown, blown in from who knows where. Around it, something remarkable: a clear ring where the bacterial colonies had dissolved. Whatever the mould was making, it was killing bacteria. Fleming's response has entered legend: not "Eureka" but a mild "That's funny."

The luck involved was almost absurd, and scientists have enjoyed listing it ever since. The mould was a rare strain of Penicillium, possibly drifting up from an allergy researcher's lab a floor below. The plate had escaped the disinfectant bath. And that fortnight's London weather had been unusual — cool days that favoured the mould, warmer days that grew the bacteria — in the exact sequence that produced a visible killing ring. A tidier man, a different fortnight, one floor's difference in the building: no ring, no story.

Fleming did real work on his discovery — he grew the mould, showed its "juice" killed many dangerous bacteria while sparing white blood cells, and named the active substance penicillin. But he could not purify it: the compound was unstable and vanished during every attempt at concentration. He concluded it would probably be useful as a laboratory tool, perhaps as a local antiseptic, published a paper in 1929 that attracted almost no attention — and, by the mid-1930s, had largely moved on. The most important medicine of the twentieth century sat in a journal, overlooked, for a decade.

The story restarts in 1938, in Oxford, when a team led by the Australian pathologist Howard Florey and the German-Jewish refugee chemist Ernst Chain went hunting through old journals for natural antibacterial substances — and found Fleming's forgotten paper. What followed was everything the legend leaves out: two years of brutal chemistry to purify the unstable compound, with the endlessly inventive Norman Heatley improvising equipment from bedpans, biscuit tins, milk churns and a bathtub, because wartime Britain could spare nothing. In May 1940 came the pivotal experiment: eight mice infected with lethal streptococci; the four given penicillin lived, the four without died overnight. Florey, not a dramatic man, called it a miracle.

Then the first human. In February 1941, Albert Alexander, a 43-year-old Oxford policeman, was dying of a raging infection that had begun — so the famous telling goes — with a scratch from a rose thorn; it had cost him an eye and was consuming his face and lungs. Given penicillin, he began to recover within days — visibly, astonishingly. But the team's entire stock was so small that they collected his urine each day to re-extract and re-inject the drug. After five days the penicillin ran out. The infection returned, and Alexander died. The lesson was written in one man's fate: the medicine worked, and a dose too small to finish the job was a death sentence. They resolved to treat children next — smaller bodies, smaller doses — until there was more.

"More" meant industry, and Britain at war had no capacity to build it. In the summer of 1941 Florey and Heatley flew to the United States — carrying the mould, with spores famously smeared into their coat linings in case the samples were lost — and lit the fuse of one of history's great scale-ups. American laboratories found better production methods (a mouldy melon from a market in Peoria, Illinois supplied a far more productive strain), corn-processing waste proved a perfect growth medium, and pharmaceutical companies, pushed by the war effort, turned mould juice into an industry. Output rose from enough for one patient in 1941 to millions of doses by D-Day in June 1944, when penicillin landed in Normandy alongside the troops. Infected wounds, which had killed soldiers by the hundred thousand in the previous war, had met their answer.

In 1945 the Nobel Prize went, justly, to three people: Fleming, Florey and Chain. But the public story had already been written otherwise. Fleming — modest, quotable, attached to a hospital with an energetic press operation — became the lone genius of the dirty dish; Florey, who distrusted journalists and refused most interviews, watched the decade of Oxford labour compress into a footnote. Historians have been redistributing the credit ever since, and the pattern has a name in the sociology of science: the world prefers one discoverer and one lightning bolt to a team and a decade. It is worth asking, every time you hear any discovery story, whose years of unphotogenic work the lightning bolt is hiding.

Fleming used his fame for one thing above all: a warning. In his Nobel lecture he described exactly how penicillin would fail — a careless public under-dosing itself, bacteria surviving exposure and breeding resistance — and events have followed his script with grim fidelity. Resistant strains appeared within years; today, drug-resistant infections kill on the order of a million people annually, and the World Health Organization lists antibiotic resistance among the gravest threats to global health. The accident gave us the antibiotic era; nothing guarantees the era is permanent.

Which returns the story to its favourite question: was it luck? The mould was luck. Everything else was selection: Fleming was the one man in the building who would look twice at a ruined plate; Florey's team was the one group in Europe systematically mining old journals for exactly such curiosities; Heatley's bedpans and the Peoria melon were improvisation, not fortune. Chance dealt one card, and a series of prepared minds played it perfectly across sixteen years. Pasteur's line remains the best summary the story has: chance favours the prepared mind — to which this story adds a correction, because the mind that was prepared was never just one man's.