When was penicillin first successfully used to treat a patient?

Penicillin was first successfully used to treat a patient in 1941, after the antibiotic’s medical potential had been demonstrated in laboratory studies. The first recorded human treatment is generally associated with Howard Florey, Ernst Boris Chain, and their Oxford team. Their work built on Alexander Fleming’s 1928 discovery of penicillin, but it took more than a decade to turn the fungus-derived substance into a usable medicine. This milestone helped launch the antibiotic era and transformed treatment of bacterial infections worldwide.