Alexander Fleming

Chapter 1 · From an Ayrshire Farm to Paddington

An inheritance, and a water polo match

1881 – 1914 · Lochfield, Ayrshire · London

Alexander Fleming was born on 6 August 1881 at Lochfield, a hill farm in Ayrshire, the seventh of his father's eight children. His father died when he was seven. He walked several miles to school and later credited a childhood spent observing the natural world with training his eye.

At thirteen he followed older brothers to London, studied at the Regent Street Polytechnic, and then worked for four years as a shipping clerk, which he disliked. In 1901 a legacy from an uncle made medical school possible.

His choice of school was, by his own account, close to arbitrary: he picked St Mary's in Paddington because he had played water polo against them. He turned out to be an exceptional student, winning the school's prizes and qualifying with distinction in 1906.

He intended to become a surgeon. He stayed instead in the inoculation department under Sir Almroth Wright, a pioneer of vaccine therapy — partly, according to the department's own tradition, because the captain of the rifle club wanted to keep a good marksman on the team. He was a lifelong enthusiast for competitive shooting and games.

He also had a playful streak that mattered scientifically: he made pictures in Petri dishes by planting different pigmented bacteria to grow into shapes and colours, which required an unusual familiarity with how colonies behave and what an unexpected growth looks like.

Why this matters

Fleming's habit of noticing what was odd in a culture dish — cultivated partly through his 'germ paintings' — is exactly the skill the 1928 observation required.

You have met the young bacteriologist. What would you ask him?

Ask Fleming

• “How did a shipping clerk end up at medical school?”
• “Did you really choose St Mary's because of water polo?”
• “What were your bacterial paintings?”
• “Why did you stay in bacteriology instead of becoming a surgeon?”
• “What did growing up on a Scottish farm teach you?”

Chapter 2 · Antiseptics That Killed the Patient

Wartime wounds, and a discovery from his own nose

1914 – 1922 · Boulogne · London

During the First World War, Fleming served with the Royal Army Medical Corps in a laboratory in Boulogne, working on infected wounds. Standard practice was to flood deep wounds with strong antiseptics.

He designed an elegant demonstration that this was wrong. Using glass tubes shaped to mimic the jagged cavities of a shrapnel wound, he showed that antiseptic failed to reach bacteria in the depths, while destroying the patient's own white blood cells, which were the body's most effective defence. Wounds treated aggressively with antiseptic often did worse.

He published the finding. Most surgeons ignored it, and men continued to die of sepsis. It left him convinced that what medicine needed was something that killed bacteria without harming human tissue — the exact criterion penicillin would later meet.

In 1921, working with a cold, he let some of his own nasal mucus fall onto a bacterial culture and noticed days later that the bacteria near it had dissolved. He had found lysozyme, an enzyme present in tears, saliva and egg white that breaks down bacterial cell walls. It was a genuine discovery and it delighted him — he collected tears from colleagues and even from children paid to cry, and long considered it his best work.

Its limitation was fatal to its usefulness: lysozyme is effective mainly against harmless bacteria and does little against the organisms that kill people. But the experience meant that when a culture plate cleared for a second time, he knew exactly what he was looking at.

Why this matters

Fleming's wartime work showed that a treatment can be actively harmful while appearing scientific — and lysozyme trained him to recognise a zone of killed bacteria on sight.

You have the training that made 1928 possible. What would you ask him?

Ask Fleming

• “Why were antiseptics making wounds worse?”
• “Why did surgeons ignore your findings?”
• “How did you discover lysozyme?”
• “Why was lysozyme not useful as a medicine?”
• “What were you actually looking for all those years?”

Chapter 3 · September 1928

A holiday, an untidy bench, and a mould from downstairs

1928 – 1929 · St Mary's Hospital, London

Fleming's laboratory was famously untidy. Before leaving for a holiday in late July 1928 he stacked culture plates of *Staphylococcus* on a bench rather than clearing them away.

Returning in early September, he sorted through them and found one contaminated by a blue-green mould. Around the mould was a clear ring where the staphylococci had been destroyed. He is reported to have said something like: that's funny.

Several coincidences were required. The mould, later identified as *Penicillium* — reclassified in modern taxonomy as *P. rubens* — probably drifted up a stairwell from a mycology laboratory on the floor below. London that summer had an unusually cool spell followed by warmth, which allowed the mould to establish first and the bacteria to grow afterwards, at exactly the temperatures each needed.

But the crucial factor was the observer. Contaminated plates were routine and were normally discarded. Fleming had spent seven years looking at exactly this phenomenon in lysozyme.

He cultured the mould, showed that the fluid it produced — which he called mould juice — killed a range of dangerous bacteria including streptococci and diphtheria, and confirmed it was not toxic to white blood cells or to rabbits. He named it penicillin in March 1929 and published in the *British Journal of Experimental Pathology*.

The paper attracted almost no attention. Fleming was not a chemist, penicillin was unstable and present in tiny quantities, and repeated attempts to purify it failed. He used it locally as an antiseptic on a few patients, presented it without persuading anyone, and by the late 1930s had largely put it aside — though he kept the culture alive and distributed samples to anyone who asked.

“One sometimes finds what one is not looking for.”

— Attributed to Alexander Fleming, quoted in obituaries and later accounts of the penicillin discovery

Why this matters

The penicillin observation shows why 'accidental' discoveries are not really accidental: the conditions were chance, but recognising what the plate meant required years of specific expertise.

You have the famous plate. What would you ask him?

Ask Fleming

• “What did you see on the plate that others would have thrown away?”
• “How much of this was luck?”
• “Why could you not turn penicillin into a drug?”
• “Why did your 1929 paper attract so little attention?”
• “Why did you keep the mould culture going for a decade?”

Chapter 4 · The Oxford Team

Florey, Chain, Heatley and a policeman named Albert Alexander

1938 – 1945 · Oxford · Peoria, Illinois

In 1938 at Oxford, the pathologist Howard Florey and the biochemist Ernst Chain — a refugee from Nazi Germany — began systematically surveying antibacterial substances and came across Fleming's paper.

The problem was chemistry, and its solution belongs largely to Norman Heatley, a young biochemist who devised a counter-current extraction method to recover the fragile compound and improvised production apparatus from bedpans, biscuit tins and milk churns because there was no money and a war on.

On 25 May 1940 the team infected eight mice with lethal streptococci and treated four with penicillin. The next morning the four treated mice were alive and the untreated ones were dead. Florey called it a miracle.

Human trials required vastly more material. The first patient, in February 1941, was Albert Alexander, a forty-three-year-old Oxford police constable with an overwhelming infection. He improved dramatically within a day. The supply — recovered and re-extracted from his own urine to eke it out — ran out. The infection returned and he died.

Britain's chemical industry was fully committed to the war, so Florey and Heatley flew to the United States in 1941. A laboratory in Peoria, Illinois, found that corn steep liquor boosted yields enormously and that a mould from a mouldy cantaloupe from a local market produced far more penicillin than Fleming's strain. American pharmaceutical companies scaled it to industrial deep-tank fermentation, and by the D-Day landings in June 1944 enough was available to treat Allied casualties.

The 1945 Nobel Prize went to Fleming, Chain and Florey. Heatley, without whom there would have been nothing to test, was not eligible because the prize can be shared by no more than three. Oxford awarded him the first honorary doctorate of medicine in its history in 1990.

Why this matters

Penicillin required an observation, a purification method and an industrial process — a standard illustration that turning a discovery into a medicine is a different job from making it.

You have the team that made it a drug. What would you ask him?

Ask Fleming

• “What did the Oxford team do that you could not?”
• “Who was Norman Heatley and why is he forgotten?”
• “What happened to Albert Alexander?”
• “Why did production have to move to the United States?”
• “Was it fair that the Nobel Prize left Heatley out?”

Chapter 5 · The Warning

What he said in Stockholm in 1945

1945 – 1955 and after · Stockholm · London

Fleming became world-famous almost overnight in 1944 and 1945, partly because the press found a lone-genius story easier to tell than a decade of collaborative biochemistry. He was knighted, given honorary degrees by dozens of universities, and made a freeman of many cities. He generally credited Florey's team when asked, and Florey — who disliked publicity intensely — did not compete for the coverage.

His Nobel lecture in December 1945 contains the most consequential thing he ever said in public. He warned that penicillin could be made to fail: it was easy to make microbes resistant in the laboratory by exposing them to concentrations too low to kill them, and the same thing would happen in the body. He described a hypothetical man who takes an insufficient dose, harbours resistant organisms, passes them to others, and ends with someone dying of an infection that penicillin can no longer touch. He added that anyone who thoughtlessly plays with penicillin treatment may be morally responsible for that death.

That was in 1945, before mass civilian use had properly begun. Resistant staphylococci appeared within a few years, and antimicrobial resistance is now among the most serious threats in global health, with the World Health Organization treating it as a leading cause of death worldwide.

Fleming died of a heart attack on 11 March 1955, aged seventy-three, and is buried in St Paul's Cathedral.

Penicillin and the antibiotics it opened the way to have saved an estimated hundreds of millions of lives, and made routine surgery, childbirth and cancer treatment survivable in ways they had never been.

Why this matters

Fleming publicly identified the mechanism of antibiotic resistance at the moment of his greatest triumph, which makes today's crisis a failure to act on a warning rather than an unforeseen surprise.

You have the warning and the fame. What would you ask him?

Ask Fleming

• “What exactly did you warn about in your Nobel lecture?”
• “How does an under-dose create resistant bacteria?”
• “Why did the press make you the sole hero?”
• “What would you say about antibiotic use today?”
• “Which of your discoveries did you value most?”

What Fleming changed

Penicillin began the antibiotic era, transforming bacterial infection from a common cause of death into a treatable condition and making modern surgery, chemotherapy and intensive care possible. Fleming's 1945 warning about resistance also defined the central problem that antibiotic medicine now faces.

A debate that continues

Historians of medicine emphasise that the popular story overstates Fleming's role and understates the Oxford team — particularly Norman Heatley, whose extraction methods made the drug possible and who was excluded from the Nobel Prize.

Keep exploring — ask Fleming

• “How do you tell a contamination from a discovery?”
• “What did the war years change about how medicine was developed?”
• “What should be done differently with the next new antibiotic?”

Related lives

• Louis Pasteur — Father of Germ Theory
• Florence Nightingale — The Lady with the Lamp
• Marie Curie — Two-Time Nobel Laureate

Related themes

Antibiotics and infection · Microbes and disease · Evolution and resistance