Antibiotic, AN tee by AHT ihk or an tih by AHT ihk, is a drug produced by certain microbes. Antibiotic substances are obtained from bacteria and fungi that live in the air, soil, and water. Most antibiotics are used by physicians to fight various diseases caused by harmful microbes. A few are used to treat certain cancers.
Antibiotics are selectively toxic--that is, they damage certain types of cells, but do not damage others. Many antibiotics are harmful to the cells of pathogenic (disease-causing) microbes, but they do not normally damage human cells. Physicians use these types of antibiotics to treat a variety of bacterial diseases, including gonorrhea, syphilis, and tuberculosis, and infections caused by staphylococcal and streptococcal bacteria. A small number of antibiotics, however, were developed to attack human cells. Some of these are used to treat cancer. They are selectively toxic mostly because they only damage cells that are in the process of dividing.
Antibiotics are sometimes called "wonder drugs" because they can cure many diseases that once were often fatal. The number of deaths that are caused by meningitis, pneumonia, and scarlet fever has declined drastically since people began using antibiotics.
Excerpt from the "Antibiotic" article, The World Book Encyclopedia © 1999