The concept of using chemicals to kill bacteria (and thus treat infections) has been around for centuries.
Malaria was treated with the bark of the cinchona tree (the precursor to quinine), and syphilis was treated with various heavy metals such as mercury and bismuth.
The first of the “modern day” antibiotics were sulphur containing compounds – the first sulphur containing drug, prontosil rubrum, was used to treat human infection in 1935.
Penicillin was discovered in 1928 by Sir Alexander Fleming, when he noticed that some bacteria that he was cultivating would not grown if a certain fungus was nearby.
This fungus was called Penicillium, and the substance elaborated by the fungus was the precursor to penicillin.
However, it was not until 1940 that penicillin was purified, and used as an antibiotic. Its availability in the latter stages of World War II saved the lives of numerous soldiers.