when was penicillin discovered

Penicillin was discovered in 1928 by Scottish bacteriologist Alexander Fleming at St. Mary’s Hospital in London.

Quick Scoop

• Year of discovery: 1928, often specifically dated to late September when Fleming noticed bacteria-killing mould on a culture plate.

• Who discovered it: Alexander Fleming, a bacteriologist working with staphylococcal bacteria.

• Where it happened: St. Mary’s Hospital (now part of Imperial College) in London.

A Bit Of Story

Fleming came back from a holiday in early September 1928 and noticed that one of his Petri dishes had grown a contaminating mould surrounded by a clear zone where bacteria would not grow.

He identified the mould as belonging to the Penicillium genus and named the active antibacterial substance penicillin , showing it could kill staphylococci and other gram‑positive bacteria.

After The Discovery

• In the late 1930s, a team at Oxford led by Howard Florey and Ernst Chain figured out how to grow the mould at scale and purify usable penicillin.

• By 1940–1941, they demonstrated its effectiveness in animals and then humans, opening the modern era of antibiotics and transforming treatment of bacterial infections.

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