Antibiotics are substances that inhibit the growth of or destroy bacteria that cause infection. Antibiotics do not work against viral diseases such as the common cold or influenza. The word "antibiotics" comes from the Greek anti("against") and bios("life"). Antibiotics have been used since the 1930s to prevent or treat a wide variety of infections in plants, animals, and humans. Before that time, there were few effective ways of combating microbial infections (infections caused by microorganisms). Illnesses such as pneumonia, tuberculosis, and typhoid fever were essentially untreatable. Even minor infections could be deadly.

The years between 1928 and 1940 were the most productive in the discovery and development of antimicrobial drugs. In 1928 Sir Alexander Fleming, a Scottish physician, was working on ways to kill bacteria isolated from infected wounds. He observed that a mold growing in a laboratory culture was able to destroy that culture's bacteria. Since the mold...