But Fleming couldn't extract the bacteria-killing substance, so he couldn't try it as a treatment for general infections. He moved on to other research - leaving Howard Florey and his team to pave the way for penicillin's use as a lifesaver more than a decade later. An antibiotic is a drug produced by microbes. Penicillin is obtained in a number of forms from Penicillium moulds. Penicillin G is the most widely used form, and is the one that killed bacteria during Duchesne's work in 1896, Fleming's work in 1928 and Florey's work in 1939.
Bacteria reproduce by dividing to produce two new cells.
They enlarge to about twice their size before the DNA chromosome is copied. The two new chromosomes move apart and a cell wall forms between them. But if penicillin is around the new cell wall won't be able to form. This means the bacteria can't reproduce, so the disease can't spread. Natural penicillin is administered by injection, because if it's swallowed stomach acids destroy the drug before it reaches the bloodstream.