The Mould that Saved Millions

On Monday 3 September 1928, Alexander Fleming saw something that would later revolutionise modern medicine and save countless lives. His finding opened the way to treating deadly infectious diseases and enabled the development of surgery, organ transplantation and cancer chemotherapy. He discovered penicillin.

It’s often described as an accidental discovery, yet Fleming could have easily overlooked what he saw that day. Natural curiosity together with astute observation form the foundation of scientific enquiry. To some degree in science you make your own luck. So chance observation or moment of genius?

That Fleming was a researcher at all, was serendipitous. You could describe him as an accidental researcher. He had planned to train as a surgeon when he graduated with a medical degree from St Mary’s Hospital in London in 1908. Two years earlier, while he was still studying, Fleming was persuaded to take a temporary job as a junior research assistant by fellow doctor, John Freeman. Freeman was an enthusiastic member of St Mary’s Rifle Club, which needed some new talent for various shooting competitions. Fleming, as it happened, was a brilliant marksman, and Freeman was keen to find reasons for him to stay. In fact, Fleming remained a member of the Inoculation Department at St Mary’s Hospital for the next 49 years.

Alexander Fleming at his cluttered laboratory bench.
Fleming would leave his culture plates for a few weeks until there were forty or fifty on his laboratory bench.

The Day that Changed the World

Imagine the scene. Fleming had returned to work at St Mary’s Hospital Medical School after a summer holiday with his family at their country home in Suffolk. The newly promoted Professor of Bacteriology sat at his cluttered laboratory bench and began to sort through a stack of petri dishes (culture plates) containing cultures of a common bacterium known as Staphylococcus aureus. Fleming would often leave petri dishes containing cultures on his bench for several weeks to see what happened to them. Not surprisingly, he found a number of petri dishes were contaminated with yeasts and moulds. Then a visitor arrived at the laboratory.

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