Which antibiotic was discovered by Alexander Fleming in 1928?

Alexander Fleming discovered the antibiotic penicillin in 1928.

Working at St Mary’s Hospital in London, Fleming noticed on 3 September 1928 that a mold contaminating a culture of Staphylococcus bacteria had created a clear zone where the bacteria would not grow. He identified the mold as belonging to the Penicillium genus and named its antibacterial substance penicillin.

Fleming published his findings in 1929, but turning the discovery into a practical medicine took another decade. Researchers at Oxford, notably Howard Florey, Ernst Chain, and their colleagues, developed methods to purify and mass-produce penicillin. Large-scale production during World War II helped make it a lifesaving treatment for wounded soldiers and civilians.

People often credit Fleming alone with “inventing” penicillin. More precisely, he discovered its antibacterial action; later scientists transformed that observation into a usable drug. Penicillin also does not treat viruses, so it cannot cure illnesses such as influenza or the common cold.