penicillin: Quick Facts

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Oct. 18, 2026

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Penicillium notatum and penicillin

hypersensitivity to penicillin

How penicillin was discovered and developed

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See how Alexander Fleming discovered penicillin

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Topics

Today in History—September 3: Alexander Fleming Finds Penicillin semisynthetic penicillin Penicillin G ampicillin Methicillin Penicillium rubens Competitive inhibition Penicillium chrysogenum Penicillium notatum Penicillium aminoglycoside tetracycline macrolide cephalosporin chloramphenicol antineoplastic antibiotic polymyxin erythromycin lincosamide oxazolidinone

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Key People

Sir Alexander Fleming sits holding a petri dish in one hand, wearing a suit and bow tie, with papers stacked beside him.

Alexander Fleming

Scottish bacteriologist

Sir Ernst Boris Chain seated in a suit, looking toward the camera with hands clasped in his lap.

Sir Ernst Boris Chain

British biochemist

Howard Walter Florey

Howard Walter Florey, Baron Florey

Australian pathologist

Robert Burns Woodward, 1966

Robert Burns Woodward

American chemist

Dorothy Crowfoot Hodgkin

Dorothy Hodgkin

English chemist

Sir Robert Robinson

Sir Robert Robinson

British chemist