The discovery of penicillin

by Aramis Schwanka Trevisan, Parikshat Sirpal and Yousef Vahabzadeh Jamairan

  Parikshat Sirpal is a PhD candidate at Polytechnique School of Montreal in Biomedical Engineering

Parikshat Sirpal is a PhD candidate at Polytechnique School of Montreal in Biomedical Engineering

  Aramis Schwanta Trevisan and Yousef Vahabzadeh Jamairan are PhD Candidates at Polytchnique School of Montreal in Electrical Engineering

Aramis Schwanta Trevisan and Yousef Vahabzadeh Jamairan are PhD Candidates at Polytchnique School of Montreal in Electrical Engineering

Probably most of us couldn’t imagine a world without antibiotics. Sometimes, when we are not feeling well, all it takes are some antibiotics pills and the problem is gone. However, it was not always like this. In fact, the story of our modern antibiotics is less than 100 years old. One of the most widely used forms of antibiotics is “penicillin”. 

The discovery of penicillin in 1928, now a well known and studied antibiotic, came about by the experience of Alexander Fleming, a creative Scottish scientist and physician who worked arduously in the laboratory and the battlefield hospitals of World War I. His search for an effective antibacterial agent, spanned many years and included a lot of dedication and hardwork, a tincture of happenstance, and a modicum of luck. It all started when Fleming was working as an Army physician during World War I and he witnessed many soldiers die of battle wounds and resulting infections.

However, what most people don’t know is that the invention of “penicillin” was a bit of an accident [1]. Story says that Alexander was out of his laboratory in the basement of St Mary’s Hospital in London for a period (some people say he just went on vacation for some time [2]) and when he came back, he noticed that one his experiments devices was accidentally left open and got contaminated by a blue-green mould from an open window. 

He could probably just have had thrown this device out. In that case, “penicillin” wouldn’t have been discovered on that Friday, September 28th, 1928 ([3]). However, he noticed that the bacterial growth of his experiment, which was left open, was significantly reduced by the presence of the mould. He then investigated and concluded that the mould was able to release a substance, which avoid and also lyses the bacteria. And that substance was “penicillin”, better known to be “Penicillium notatum”. 

According to [4], Fleming was known to be a poor communicator and orator. As a consequence, his studies were not very known by the scientific community. [4] also states that if Alexander Fleming had been more successful in making other scientist interested in his work, probably the penicillin would have been discovered much earlier.

The medical treatments at the time effectively hampered the patient’s immunological defenses more than killing the invading bacteria. Thus, this combined with his medical expertise and innate creativity, Fleming devised an ingenious experiment in which he was able to isolate an important enzyme, lysozyme. However, this did not have much impact as a therapeutic modality. However, Fleming had been investigating the properties of various bacterial species and had stacked cultures of staphylococci on a bench in a corner of his laboratory. Fleming noticed that one culture was growing a fungal species and the previous bacterial colonies surrounding the fungus had been destroyed, but other bacterial colonies farther away from the fungus were normal. Fleming continued to grow this new substance which he gave the name of “mould juice” and found that it was able to kill disease-causing bacteria. He later called it penicillin in March 1929.

His discovery had immediate impact on diseases such as scarlet fever, pneumonia, meningitis and gonorrhoea. By the end of 1944, mass production of penicillin began and eventually enough penicillin had been produced to treat all the wounded with the Allied forces.

Many aspects of modern medicine and pharmacotherapeutics now hinge on the discovery of penicillin. The implications of this discovery are now well known but in 1928, it was indeed revolutionary. Fleming himself said:

"When I woke up just after dawn on September 28, 1928, I certainly didn't plan to revolutionise all medicine...But I suppose that was exactly what I did." 

When implanting bacteria on a dish, he saw that it was a transparent area. Unlike other scientists, he didn’t throw the dish away but instead he attempted to find the reason why the bacteria in that area was killed.


Bud, Robert (2009). Penicillin: Triumph and Tragedy. Oxford University Press. 

Reader’s digest: 10 accidental inventions and the funny stories behind them. Available at:

Haven, Kendall F. (1994). Marvels of Science: 50 Fascinating 5-Minute Reads. Littleton, CO: Libraries Unlimited. p. 182

Lax, Eric (2004). The Mold in Dr. Florey's Coat: The Story of the Penicillin Miracle. Holt Paperbacks.