Advances in Medicine, Surgery and Public Health, 1920-48: The NHS » Fleming and the Discovery of Penicillin

A world without cures

By the 1920s, Pasteur, Koch and others had shown that germs cause many diseases. Antiseptics could clean wounds and surgeons used aseptic methods, but doctors still had almost nothing that could kill bacteria inside the body. Antiseptic chemicals strong enough to kill germs also harmed the patient's own cells. Ehrlich's Salvarsan worked against syphilis only. A scratch, a sore throat or an infected wound could still turn into blood poisoning or pneumonia and kill. Medicine badly needed a safe drug that attacked bacteria.

Key terms:

• Penicillin: a substance made by the mould Penicillium that kills many kinds of bacteria.
• Bacteriologist: a scientist who studies bacteria.
• Antibiotic: a medicine, made from a living organism such as a mould, that kills bacteria inside the body. Penicillin was the first widely used antibiotic.

Fleming's discovery, 1928

Alexander Fleming was a Scottish bacteriologist who worked at St Mary's Hospital in London. In the First World War he served in the army medical corps and saw soldiers die from infected wounds. Afterwards he spent years looking for something that would kill germs without harming the body.

In September 1928 Fleming came back from a holiday to his untidy laboratory. He had left dishes of Staphylococcus bacteria, which cause boils and wound infections, stacked on a bench. On one dish a blue-green mould had grown. Fleming noticed that the bacteria had been killed in a clear ring around the mould. Something the mould was making was destroying the germs.

Fleming did not just throw the dish away. He grew more of the mould, identified it as a type of Penicillium, and called the liquid it produced "penicillin". Chance played a part: the mould drifted onto the dish and the conditions were right. But a scientist who had not been looking for a germ-killer might have ignored it. Fleming spotted its importance, and that is why he is remembered.

The 1929 paper

In 1929 Fleming published his results in a scientific journal. He reported that penicillin killed many kinds of harmful bacteria, including those behind some wound infections, and that it did not seem to harm white blood cells, which are part of the body's defences. He suggested it might be useful as an antiseptic on infected wounds. He also found it useful in the laboratory, because it killed unwanted bacteria and let him grow other germs on their own.

Why was penicillin not followed up?

Penicillin did not become a medicine until around ten years later. There were several reasons.

• It was very hard to make. The mould produced only tiny amounts of penicillin, and it was difficult to separate from the liquid around it. It also broke down easily. Fleming was a bacteriologist, not a chemist, and he could not purify it himself.
• Doubts about its power. Fleming saw it mainly as an antiseptic for surface wounds. He worried that it might not last long enough in the blood to fight deep infections, and he did not prove that it could cure an illness inside the body.
• Little interest from others. His 1929 paper was published but drew little attention. No team of chemists was working with him, and no drug company took it up.

By the 1930s Fleming had mostly moved on to other work. The discovery sat waiting until other scientists took it up in 1939-40 (the subject of the next lesson).

Change and continuity: Fleming's discovery was a major change, because it pointed to a drug that could kill bacteria inside the body, which nobody had managed before. But for about a decade nothing in everyday medicine changed. Doctors still had to rely on rest, nursing and clean surroundings, as they had in the 1900s.

Common mistakes

Exam-style question

Explain TWO causes of the delay in turning penicillin into a medicine after Fleming's discovery in 1928. [8 marks]

(Tip: one cause alone can score no more than 4 marks, so always give two.)