Penicillin is one of the most important medical discoveries of our time, for it allows doctors to easily treat illnesses and infections that once killed many people.
If it weren’t for penicillin and other drugs like it, there would be little a doctor could do for you if you came down with a very bad cold or a serious infection.
Centuries ago, moldy bread was sometimes used as an antiseptic, but no one knew why mold could kill germs. Late in the 19th century, scientists discovered that certain molds and bacteria produced substances that would kill or prevent the growth of other bacteria. These substances are now called antibiotics.
Then, in 1928, an English scientist named Alexander Fleming was working in his laboratory with a culture of bacteria. When a kind of mold, called penicillium, accidentally infected the culture, Fleming noticed that the mold killed the bacteria around it. Further experiments showed that these molds produced a substance that would kill many common bacteria, and Fleming named the substance
What was most important about penicillin was that it did not harm living body cells, as did the antibiotics discovered before that. In 1939, other scientists found a way to purify and strengthen penicillin, and it became available in the United States in the 1940s.