Penicillin G (Benzylpenicillin)


Penicillin G (Benzylpenicillin)


3D-model of benzylpenicillin


3D-model of benzylpenicillin

Penicillin G benzathine is an antibiotic used to treat a variety of bacterial infections.

Inventor of Penicillin: Sir Alexander Fleming

Sir Alexander FlemingSir Alexander Fleming was born at Lochfield near Darvel in Ayrshire, Scotland on August 6th, 1881. He attended Louden Moor School, Darvel School, and Kilmarnock Academy before moving to London where he attended the Polytechnic. He spent four years in a shipping office before entering St. Mary’s Medical School, London University. He qualified with distinction in 1906 and began research at St. Mary’s under Sir Almroth Wright, a pioneer in vaccine therapy. He gained M.B., B.S., (London), with Gold Medal in 1908, and became a lecturer at St. Mary’s until 1914. He served throughout World War I as a captain in the Army Medical Corps, being mentioned in dispatches, and in 1918 he returned to St.Mary’s. He was elected Professor of the School in 1928 and Emeritus Professor of Bacteriology, University of London in 1948. He was elected Fellow of the Royal Society in 1943 and knighted in 1944

arly in his medical life, Fleming became interested in the natural bacterial action of the blood and in antiseptics. He was able to continue his studies throughout his military career and on demobilization he settled to work on antibacterial substances which would not be toxic to animal tissues. In 1921, he discovered in tissues and secretions an important bacteriolytic substance which he named Lysozyme. About this time, he devised sensitivity titration methods and assays in human blood and other body fluids, which he subsequently used for the titration of penicillin. In 1928, while working on influenza virus, he observed that mould had developed accidently on a staphylococcus culture plate and that the mould had created a bacteria-free circle around itself. He was inspired to further experiment and he found that a mould culture prevented growth of staphylococci, even when diluted 800 times. He named the active substance penicillin.

The identification of penicillium mold by Dr. Alexander Fleming in 1928 is one of the best-known stories of medical discovery, not only because of its accidental nature, but also because penicillin has remained one of the most important and useful drugs in our arsenal, and its discovery triggered invaluable research into a range of other invaluable antibiotic drugs.

While researching the flu in the summer of 1928, Dr. Fleming noticed that some mold had contaminated a flu culture in one of his petri dishes. Instead of throwing out the ruined dish, he decided to examine the moldy sample more closely.

Fleming had reaped the benefits of taking time to scrutinize contaminated samples before. In 1922, Fleming had accidentally shed one of his own tears into a bacteria sample and noticed that the spot where the tear had fallen was free of the bacteria that grew all around it. This discovery peaked his curiosity. After conducting some tests, he concluded that tears contain an antibiotic-like enzyme that could stave off minor bacterial growth.

Six years later, the mold Fleming observed in his petri dish reminded him of this first experience with a contaminated sample. The area surrounding the mold growing in the dish was clear, which told Fleming that the mold was lethal to the potent staphylococcus bacteria in the dish. Later he noted, “But for the previous experience, I would have thrown the plate away, as many bacteriologists have done before.”

Instead, Fleming took the time to isolate the mold, eventually categorizing it as belonging to the genus penicillium. After many tests, Fleming realized that he had discovered a non-toxic antibiotic substance capable of killing many of the bacteria that cause minor and severe infections in humans and other animals. His work, which has saved countless lives, won him a Nobel Prize in 1945.


From Nobel Lectures, Physiology or Medicine 1942-1962, Elsevier Publishing Company, Amsterdam, 1964

This autobiography/biography was first published in the book series Les Prix Nobel. It was later edited and republished in Nobel Lectures. To cite this document, always state the source as shown above

Accidental Discoveries: