It’s hard to believe that one of the most widely prescribed antibiotics in the world was discovered by accident nearly a century ago in 1928. Prior to this discovery, infections such as bacterial endocarditis, bacterial meningitis, and pneumococcal pneumonia were often deadly. Penicillin’s discovery then sparked a new era of medicine where doctors finally held a powerful tool in their hands to stop the spread and fatality of infectious diseases.

 At the time, Scottish researcher Sir Alexander Fleming had been in the middle of conducting an experiment in London with the influenza virus when he went on a two week vacation. Upon his return, Fleming came back to discover that a staphylococcus culture plate in his lab had been contaminated and that a mold was now growing on the plate. When analyzed closer, he noted that this mold was actually preventing the growth of the staphylococci bacteria. This mold would later be identified as Penicillium notatum by Dr. Howard Florey.

Dr. Florey then set off to complete a number of experiments on mice in order to determine penicillin’s effectiveness in treating bacterial infections in live models. Fifty mice were infected with streptococcus, a bacteria known for causing deadly infections. The mice that were then treated with penicillin all survived while the mice not treated with penicillin died. Florey concluded that the results were promising enough to begin testing the antibiotic on people. However, Florey then faced the challenge of producing and extracting enough pure penicillin to treat each individual. When treating his first patient Albert Alexander in 1941, it took roughly 2,000 liters of the mold culture fluid to obtain an adequate amount of pure penicillin for the antibiotic. After five days of injecting the patient, Albert began to recover. Unfortunately, however, Florey’s supply of pure penicillin was depleted after these five injections, which had not been enough to successfully eradicate the infection. Albert sadly passed a few days later. The demand for penicillin was quickly beginning to significantly outweigh its limited supply. Ultimately, a new species of penicillin was discovered, Penicillium chrysogenum, which had the ability to mass produce pure penicillin for use in antibiotics. This became especially vital during World War II as penicillin was used to treat bacterial pneumonia. The death rate from bacterial pneumonia fell from 18% in WWI to less than 1% in WWII thanks to penicillin. Today penicillin is synthesized in a lab using penicillium mold, which naturally produces penicillin. The mold is grown with sugars and other ingredients through deep-tank fermentation until the penicillin is able to be separated from the mold. Once separated, penicillin can finally be purified and will be ready for use as an antibiotic.

The discovery of the world’s first antibiotic proved to be revolutionary as penicillin had the ability to attack and kill a wide range of bacteria. Infections which had previously been severe or even fatal were now being easily treated with penicillin. This discovery also led the movement in the search for other natural products with antimicrobial activity and ultimately led to the discovery of new antibiotics such as streptomycin and tetracycline. It’s hard to imagine what the world would look like today if Alexander Flemming had not left out his dirty staphylococcus plates while on vacation and ultimately discovered the mold containing penicillin. This was truly a turning point in human history which not only changed our approach to treating bacterial infections but saved millions of lives. 

Despite being one of the most widely prescribed antibiotics, penicillin is also one of the most commonly reported drug allergies. For more information regarding penicillin allergy testing, please follow the link to our Educational Resources page here.