What is penicillin, and how was it discovered?

Penicillin was first discovered in by Alexander Flemming , a scientist who was growing staphylococci a type of bacteria on agar plates. He came across penicillin by leaving the lid off his agar plates and the windows open whilst he was away on holiday. This mould was Penicillium notatum , but scaling the penicillin up to a useable level was a challenge.

They infected eight mice with bacteria which could usually kill them, but four were given penicillin. The four mice treated with penicillin stayed healthy, but the four untreated mice died.

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They then moved this theory over to humans by treating Albert Alexander, a year old policeman dying of a blood infection, with penicillin for 5 days. This did reduce the infection, but unfortunately the penicillin ran out before the infection was completely cured and Albert died. Next, Florey and Chain treated a year old boy with penicillin, after an operation which gave him an infection.

This cured the boy. But the problem was making enough of it to supply the demand of the soldiers in World War 2. In Britain, all the big laboratories and factories were busy with the war effort.