The discovery and development of penicillin
Penicillin heralded the dawn of the antibiotic age. Before its introduction there was no effective treatment for infections
such as pneumonia, gonorrhea, or rheumatic fever. Hospitals were full of people with blood poisoning contracted from a cut
or a scratch, and doctors could do little for them but wait and hope.
Antibiotics are compounds produced by bacteria and fungi which are capable of killing, or inhibiting, competing microbial species.
This phenomenon has long been known; it may explain why the ancient Egyptians had the practice of applying a poultice of moldy
bread to infected wounds. But it was not until 1928 that penicillin, the first true antibiotic, was discovered by Alexander Fleming,
Professor of Bacteriology at St. Mary's Hospital in London.
Returning from holiday on September 3, 1928, Fleming began to sort through petri dishes containing colonies of Staphylococcus, bacteria
that cause boils, sore throats, and abscesses. He noticed something unusual on one dish. It was dotted with colonies, save for one area
where a blob of mold was growing. The zone immediately around the mold - later identified as a rare strain of Penicillium notatum - was
clear, as if the mold had secreted something that inhibited bacterial growth.
Fleming found that his "mold juice" was capable of killing a wide range of harmful bacteria, such as streptococcus, meningococcus, and
the diphtheria bacillus. He then set his assistants, Stuart Craddock and Frederick Ridley, the difficult task of isolating pure penicillin
from the mold juice. It proved to be very unstable, and they were only able to prepare solutions of crude material to work with. Fleming
published his findings in the British Journal of Experimental Pathology in June 1929, with only a passing reference to penicillin's
potential therapeutic benefits. At this stage it looked as if its main application would be in isolating penicillin-insensitive bacteria from
penicillin-sensitive bacteria in a mixed culture. This at least was of practical benefit to bacteriologists, and kept interest in penicillin
going. Others, including Harold Raistrick, Professor of Biochemistry at the London School of Hygiene and Tropical Medicine, tried to purify
penicillin but failed.