The idea of antibiotics, substances that destroy or inhibit the growth of certain other microorganisms, dates back to the late nineteenth century, but the first antibiotics were not produced until well into the twentieth century.

The great French chemist Louis Pasteur (1822–1895) laid the foundation for understanding antibiotics when in the late 1800s he proved that one species of microorganisms can kill another. German bacteriologist Paul Ehrlich (1854–1915) then developed the concept of selective toxicity, in which a specific substance can be toxic (poisonous) to some organisms but harmless to others. Based on this research, scientists began working to develop substances that would destroy disease-spreading microorganisms. A breakthrough came in 1928 when Scottish bacteriologist Alexander Fleming (1881–1955) discovered penicillin. Fleming observed that no bacteria grew around the mold of the genus Penicillium notatum, which had accidentally fallen into a bacterial culture in his laboratory.

But penicillin proved difficult to extract. It was not until more than a decade later (in 1941) that the substance was purified and tested, by British scientist Howard Florey (1898–1968). Another British scientist, Ernst Boris Chain (1906–1979), developed a method of extracting penicillin, and under his supervision the first large-scale penicillin production facility was completed, making the antibiotic commercially available in 1945. That same year, Fleming, Florey, and Chain shared the Nobel prize in physiology or medicine for their work in discovering and producing the powerful antibiotic, still used today in the successful treatment of bacterial diseases, including pneumonia, strep throat, and gonorrhea.

The term “antibiotic” was coined by American microbiologist Selman A. Waksman (1888–1973), who tested about 10,000 types of soil bacteria for antibiotic capability. In 1943 Waksman discovered a fungus that produced a powerful antibiotic substance, which he called streptomycin. The following year, the antibiotic was in production for use in treating tuberculosis, typhoid fever, bubonic plague, and bacterial meningitis. Although streptomycin was later found to be toxic, it saved countless lives and led to the discovery of many other antibiotics, which have proven both safe and effective.