Alexander Fleming

Alexander Fleming (1881–1955) was a Scottish doctor and brilliant biologist, best known for discovering penicillin, the world’s first antibiotic (bacteria killer). His research helped to save millions of lives and revolutionised the treatment of wounds and common diseases. Learn more about this intelligent and dedicated scientist, and use our collection of printable resources below to test your findings.

Interesting Facts

• Alexander Fleming discovered penicillin quite by accident. He was studying the properties of a bacterium called staphylococcus, when he discovered a green mould growing in some of his samples.
• In World War I, bacterial pneumonia killed 18 per cent of wounded soldiers. In World War II, this figure fell to less than 1 per cent, thanks to the introduction of penicillin as a treatment.

Alexander Fleming Quotes

“When I woke up… on September 28, 1929, I certainly didn’t plan to revolutionise all medicine by discovering the world’s first antibiotic, or bacteria killer. But I suppose that was exactly what I did.”

“Tears, saliva and sputum… rid the body of microbes by mechanically washing them away… however, it is quite clear that these secretions… have the property of destroying microbes to a very high degree.”

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

A Short Biography of Alexander Fleming

Alexander Fleming was born in Ayrshire, Scotland, in 1881. His parents, Hugh and Grace, had both come from farming families. Alexander was one of four children, but had four half-siblings from his father’s first marriage. His father died when Alexander was just seven.

Alexander was an intelligent child and at 11 gained a scholarship to boarding school. He went for two years, but at 13, most of his family moved to London to live with his older brother Tom, while their eldest brother Hugh looked after the family farm. Alexander studied business and commerce at London’s Royal Polytechnic Institution, and went to work in a shipping office, but he loathed it.

Tom Fleming was a doctor, and with his brother’s encouragement and the help of some inheritance money, Alexander applied to study medicine at St Mary’s Hospital Medical School, where he qualified in 1906.

During his student days, Alexander joined the Territorial Army (TA). He thought he wanted to become a surgeon, but instead joined the research team in the Inoculation Department, partly to remain with his TA friends. In 1908, he graduated with a further degree in bacteriology and the gold medal for top student.

Alexander was particularly interested in the body’s natural ability to fight infection. With the outbreak of war in 1914, he joined the Royal Army Medical Corps and began working in field hospitals in France. He noticed many soldiers were dying from infected wounds because the antiseptics used to treat them were weakening the body’s natural immune system. Antiseptics were useful for small cuts, but more harmful for deep wounds. Instead, Alexander recommended bathing wounds in salt water and keeping them clean and dry.

During his time in the army, Alexander married Sarah Marion McElroy, a nurse. They went on to have a son together, Robert, who became a doctor himself in later life.

After the war, Alexander returned to St Mary’s determined to find anti-bacterial substances that could treat infections.

In 1922, Alexander realised that bodily fluids, such as tears, saliva and mucus, had antiseptic properties. He had a cold at the time, and while studying bacteria, a drop of mucus fell from his nose onto the sample. He was amazed to see that around the droplet, bacteria were being destroyed. Alexander went on to test a range of bodily fluids and found they all had an enzyme (protein), which he called lysozyme. This discovery inspired him to find a substance that would destroy even more deadly bacteria.

In 1928, Alexander returned from a month’s holiday with his wife and young son. He noticed that in his absence, samples of Staphylococcus bacteria had become contaminated, and a type of green fungus was growing. What’s more, where the mould lay, the bacteria had been destroyed – just as it had with lysozyme. Alexander called the new substance ‘mould juice’, but later named it penicillin.

Alexander tried to grow more of the fungus to identify its properties. This time it wasn’t an enzyme but a natural antibiotic that could kill different types of bacteria, including those causing meningitis, scarlet fever and pneumonia. We now know that antibiotics prevent bacteria from forming new cell walls, so they can’t grow and spread. But Alexander had difficulties isolating penicillin from the fungus and couldn’t produce it in large quantities for use as a drug.

In the early 1940s, however, a team of scientists at Oxford University, led by Howard Florey and Ernst Boris Chain, developed Fleming’s findings and managed to isolate, grow and purify penicillin into a useable drug, which was then used as an antibiotic during WWII. Alexander was knighted in 1944, and the following year he shared the Nobel Prize with Florey and Chain, for the discovery of penicillin and its use against infectious diseases.

Alexander’s wife Sarah died in 1949, and in 1953 he married Dr Amalia Koutsouri-Voureka, a Greek colleague at St Mary’s. Alexander himself died of a heart attack in 1955 at the age of 73. His ashes were buried in St Paul’s Cathedral, London, in recognition of a man who had paved the way for modern medicine. His findings had saved millions of lives, and would continue to do so in the years ahead.

Our Alexander Fleming Resources