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How Was Penicillin Discovered and Developed?

By Bronwyn Harris
Updated Mar 03, 2024
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Alexander Fleming, a Scottish bacteriologist in London, discovered penicillin by mistake when he was trying to study Staphylococcus bacteria in 1928. He was running experiments with the bacteria in his laboratory at London's St. Mary's Hospital, and set a laboratory dish containing the bacteria near an open window. Upon returning to the experiment, he found that some mold blown in through the open window onto the dish, contaminating the bacteria.

Instead of throwing away his spoiled experiment, Fleming looked closely at it under his microscope. Surprisingly, he saw not only the mold growing on the bacteria, but a clear zone around the mold. The Penicillium mold, the precursor to penicillin, was dissolving the deadly Staphylococcus bacteria.

Fleming was originally optimistic that penicillin would be useful as an antibacterial agent, as it was safe for the human body, yet potent. Later, in 1931, he changed his mind and decided that it would not last in humans for the duration needed to kill harmful bacteria, and stopped studying it. In 1934, he began another few years of clinical trials and tried to find someone else to purify it.

Researchers at Oxford University in England, including Howard Florey, Ernst Chain, and Norman Heatley, experimented with Fleming's discovery. They proved that penicillin would be both harmless and effective in mice, but did not yet have the volume needed to treat people. Orvan Hess and John Bumstead were the first people to use it to successfully treat a patient.

Penicillin saved the lives of many soldiers in World War II, but the supply was extremely limited, and the drug was rapidly excreted from the body, so the patients had to be dosed frequently. It was common practice at this point to save the urine from patients undergoing treatment so that the penicillin could be isolated and reused. Another agent, probenecid, was eventually found to prolong the duration of penicillin in the human body.

Fleming, Florey, and Chain were awarded the Nobel Prize in medicine in 1945 for the discovery and development of penicillin. Florey was openly worried about the possibility of a population explosion resulting from health care improvements and said that his work with the antibiotic was more of an interesting scientific problem than a way to help people. He did admit that the fact that it could help people was a good thing, but not why he was originally interested.

Andrew J. Moyer later discovered how to make large quantities of penicillin, patenting the process and advancing the fight against infectious diseases. In 1987, he was inducted into the National Inventors Hall of Fame for his process of creating penicillin in high quantity.

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Discussion Comments

By anon319780 — On Feb 14, 2013

'First treatment' claims for Penicillin are widely documented? In the UK, the very first treatment was given to Police Constable Albert Alexander in 1941. Sadly, the supply run out and he succumbed to his infection!

In the US, the official first patient who was saved by penicillin administered in hospital settings was Anne Miller, 90, cured in March 1942.

She had been hospitalized for a month, often delirious with her temperature spiking to nearly 107, while doctors tried everything available, including sulfa drugs, blood transfusions and surgery. All failed. Within 24 hours of treatment, the patient responded and made a complete recovery. She eventually died aged 90.

By anon288357 — On Aug 29, 2012

So this experiment led to the development of what major medical advancement? Mold, right? Or am I mistaken?

By anon253306 — On Mar 08, 2012

Why are you arguing about whose relative got the first dose -- and capitalize America, please.

By anon242284 — On Jan 22, 2012

Sir Alex was wise.

By anon163689 — On Mar 28, 2011

Who was the first person to take penicillin?

By anon155814 — On Feb 24, 2011

Completely agree with anon1008, fleming did not desire the credit. He gave up on the idea fast, believing that it could not work in humans.

When Heatley, Chain, and Florey picked it up, they turned a part of Oxford university into a penicillin production plant. It took them four years of staying up all night and working hard to get an extract.

They carried on even when they were suffering (Florey's wife died and his children got evacuated to the usa, chains sister and mum got killed in concentration camp) Heatley designed a method of extracting it with old bookcases and telephones due to war shortages.Fleming even went to the lab and observed, helping in no way and leaving without any compliments.

Heatley and Florey flew over to america to get the funding so they could mass produce and save thousands of soldiers. When the war was over, Fleming took the credit. He got the Nobel prize and was the one who got remembered.

Florey and chain got a shared nobel prize too, but were quickly forgotten. Heatley got no prizes or mentions, no one knew who he was and he spent the rest of his life traveling in a van.

By anon119521 — On Oct 18, 2010

Does anyone know how he trialed this? Thanks.

By anon101038 — On Aug 01, 2010

my girlfriend was dying and needed fast and effective treatment, and her family doctor gave her some penicillin, but she still died. it didn't work! now i lost my baby. i miss you Jill! i will never forget you!

By anon93177 — On Jul 02, 2010

Actually, my Dad was the first person in the U.S. who received penicillin as a treatment. He was in the Navy and taken to the Great Lakes Naval Hospital. His treatment was on November 6, 1943. His parents were told that it saved his life.

By anon70285 — On Mar 13, 2010

Duchesne originally discovered the antibiotic properties of Penicillium, but failed to report a connection between the fungus and a substance that had antibacterial properties, and Penicillium was forgotten in the scientific community until Fleming's rediscovery.

By anon65766 — On Feb 15, 2010

How did it change our treatment of infection?

By anon61501 — On Jan 20, 2010

My great grandfather was the first person to have penicillin. he had peritonitis which is an inflammation of the peritoneum,so he was given the first ever dose of penicillin.

By anon37621 — On Jul 20, 2009

Can anyone tell me how the horse urine myth got introduced to the penicillin? As I was growing up the story was the horse unire was collected and sold for production of penicillin. There are a few articles referring to this on line.

I know that pregnant mare urine was collected for estrogen.

Thank you for your input

By Dayton — On Sep 26, 2007

Actually, that's right. Even though Fleming is largely credited with the discovery, Duchesne seems to have discovered the antibiotic effects of penicillin about 30 years earlier, but couldn't get any academic or medical attention to his work.

By anon3962 — On Sep 26, 2007

Alexander Fleming did not discover penicillin he re-discovered because the first person was Ernest Dechesne.

By anon1022 — On May 11, 2007

Very interesting. I did not know of Dr.Florey´s concern about the demographic explosion as a consecuence of the use of penicilin. Thanks

By anon1014 — On May 11, 2007

Why wasn't Norman Heatley included in the Nobel Prize award?

By anon1008 — On May 11, 2007

Fleming did nothing about developing Penicillin following his first serendipitous observation.

After Florey, Chain and Heatley had done the real work of developing it, Fleming turned up at Oxford to take the credit.

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