On 7 March 1929, Alexander Fleming coined the word “penicillin” for the antibacterial substance produced by a Penicillium mould.
Fleming had observed that a mould contaminating a staphylococcus culture prevented bacterial growth nearby. He first referred to the material in less convenient terms such as “mould juice” and “mould broth filtrate.” He chose penicillin because the substance came from the genus Penicillium, following naming patterns such as digitalin, derived from Digitalis.
The discovery was made at St Mary’s Hospital in London after Fleming returned from vacation in September 1928 and noticed that bacteria had been destroyed around the mould colony. His early work showed that the substance was effective against several mainly Gram-positive bacteria, including staphylococci and streptococci.
Fleming published his findings in 1929, but the discovery initially attracted little attention. The Oxford team led by Howard Florey and Ernst Chain later developed methods to purify and produce penicillin, helping turn Fleming’s observation into a practical medicine.