Advances in Medicines: Magic Bullets and Antibiotics

From understanding infection to treating it

By the beginning of the twentieth century, germ theory had given scientists a clearer target for treatment: the microbes responsible for disease. Knowing what caused an infection did not automatically provide a cure, however. Researchers still had to find substances that would attack the microbes inside a patient’s body.

Two important developments were magic bullets and antibiotics. These helped medicine move towards treatments directed at the cause of an infection, rather than simply relieving its symptoms. Their development depended on laboratory experiments, individual discoveries and the ability to manufacture medicines in useful quantities.

Ehrlich and Hata: the first magic bullet

The idea of a magic bullet was a chemical that could attack disease-causing bacteria without harming the rest of the body. The name expressed the aim of a targeted treatment; it did not mean a universal cure for every illness.

Paul Ehrlich investigated arsenic compounds as a treatment for syphilis, a serious bacterial disease. By 1907, he had tested more than 600 versions without finding a successful cure. This was systematic research: scientists tested different compounds rather than relying on a single guess.

In 1909, the Japanese scientist Sahachiro Hata, working with Ehrlich, retested compound 606 and found that it treated syphilis. It became known as Salvarsan 606, the first magic bullet. Its importance lay both in treating a particular disease and in demonstrating that chemical research could produce medicines aimed at specific infections.

Domagk and Prontosil: extending chemical treatment

In 1932, Gerhard Domagk discovered that a red dye called Prontosil could combat bacterial infections in mice. This provided another example of a chemical substance being developed into a medicine.

Prontosil was subsequently used to treat serious infections, including puerperal fever, an infection associated with childbirth. At Queen Charlotte’s Maternity Hospital in London, its use was associated with a fall in the death rate from puerperal fever from 20% to 4.7%. This shows the practical importance of the new medicines: infections that had frequently been fatal became more treatable.

Salvarsan and Prontosil encouraged further searches for effective drugs. Nevertheless, the available magic bullets did not successfully treat every kind of bacterial infection.

Fleming’s discovery of penicillin

Alexander Fleming was a doctor and researcher at St Mary’s Hospital in London. He studied Staphylococcus, bacteria that could cause dangerous infections, including blood poisoning, and were not effectively treated by the magic bullets then available.

In 1928, Fleming noticed that mould had contaminated a dish containing these bacteria. Around the mould was an area where the bacteria had not grown. The important observation was not simply that mould was present, but that it appeared to prevent bacterial growth.

Fleming investigated the effect and identified penicillin. He published his findings in 1929. Chance had created the contaminated dish, but his scientific knowledge allowed him to recognise why it mattered.

Penicillin was an antibiotic originally obtained from a living microorganism, unlike the early synthetic chemical magic bullets. It could attack bacteria responsible for infection. Fleming’s discovery alone, however, did not produce a readily available medicine: further research and a reliable supply were needed before patients could benefit widely.

Florey and Chain: turning discovery into treatment

At Oxford, Howard Florey and Ernst Chain took up Fleming’s work in 1939. Their team developed penicillin further and successfully tested it on mice in 1940. These experiments provided evidence that it could work as a treatment, not just prevent bacteria growing in a laboratory dish.

In 1941, they treated Albert Alexander, a policeman suffering from a severe infection. His condition improved, but the team could not produce enough penicillin to complete his treatment. Their supply ran out and he died.

This case revealed both the promise and the practical limitation of the medicine. An effective substance was not enough: doctors needed sufficient quantities to treat patients fully. The next challenge was therefore production.

War, government and industry: making penicillin widely available

In July 1941, Florey travelled to the United States to seek help from pharmaceutical companies. The Second World War created urgent demand for a medicine that could prevent wounded soldiers from dying of infection.

British and American government support helped research and production, while pharmaceutical companies supplied the industrial capacity to manufacture penicillin on a much larger scale. Large production vessels, including vats, increased the supply beyond what a small research team could make.

By 1945, the US Army had access to around two million doses a month. Penicillin could now be used widely to treat wounded soldiers. This was a connected process: Fleming’s observation provided the starting point, the Oxford team demonstrated its value as a treatment, and government support and industrial technology made mass production possible.

Further progress—and the limits of antibiotics

Penicillin was followed by other antibiotics. Streptomycin, discovered in 1943, provided a treatment for tuberculosis. In 1945, Dorothy Hodgkin worked out penicillin’s chemical structure; John C. Sheehan made a chemical copy in 1957. These developments show how scientific understanding could help researchers move beyond extracting a medicine from its original source.

Antibiotics became available in forms such as capsules and injections, and drug trials checked effectiveness and side effects. Treatment of bacterial infection had changed greatly, but antibiotics were not a cure for every disease.

One continuing problem is antibiotic resistance. Some bacteria can survive a medicine that previously worked against them, making infections harder to treat. Penicillin-resistant strains appeared as early as 1942, and overuse of antibiotics has contributed to the problem. Modern medicines therefore represent a major advance in treatment, not the complete defeat of infectious disease.