Alexander Fleming discovered penicillin in 1928. Penicillin stopped the growth of disease-carrying bacteria. Thus it could help cure illnesses caused by these bacteria. In the years after Fleming's discovery, other substances were discovered to have similar effects. Streptomycin, which was discovered in 1944, attacked bacteria that could resist penicillin. All of these substances are called antibiotics, and after 1945 they transformed the fight against disease. They cured certain illnesses, such as tuberculosis, that previously could not be treated, and they made surgery safer from infections. Antibiotics were also used to improve the health of animals that are used for food. Although some bacteria came to resist antibiotics, these substances became essential in reducing sicknesses and providing more food.
