The discovery and development of an antibiotic.

The story is of course a classic in the history of science. Sir Alexander Fleming (1881-1951), working in 1928 at St Mary's Hospital, Paddington was using cultures of the bacterium Staphylococcus on agar. He noticed that one plate on which there a number of colonies of bacteria had become contaminated with a mould fungus, Penicillium notatum. (In fact, Fleming named the fungus P. rubrum; it was identified by others in 1930 as P. notatum). Adjacent to the spreading fungal mycelium, growth of the bacterial colonies was inhibited. Further away, the bacterial colonies were growing normally. Fleming reasoned that a water soluble antibacterial chemical was being secreted by the mould and diffusing within the agar around the mould colonies. He named the substance penicillin. He subsequently found that when the fungus was cultured in a nutrient broth, it destroyed many pathogenic microorganisms. His outstanding achievement was this discovery. It was more than ten years later that Florey and Chain were able to exploit the recently developed technique of freeze-drying to concentrate the unstable compound successfully, from the culture medium containing the fungus, and make a pure preparation of penicillin.

Initially, the fungus was cultured in flasks, and even milk bottles, an extremely laborious, labour intensive process. Only later were strains of Penicillium developed that were productive enough in liquid media to open the way for large scale production in fermenters.

It was not until 1941 that penicillin was produced on a reasonably large scale by an Anglo-American partnership, huge impetus being provided by the need to treat casualties of the Second World War. The development was just in time for the lives thousands of injured servicemen and women, as well as civilians, to be saved.

Fleming, Florey and Chain subsequently shared a Nobel Prize for their work.