A chemical that kills or reduces the reproduction rates of organisms.<ref>Wile, Dr. Jay L. Exploring Creation With Biology. Apologia Educational Ministries, Inc. 1998</ref> Such chemicals may be secreted by living organisms (such as penicillin, which is produced by certain molds) or they may be artificially synthesized.
Category of Drugs Category of Antibiotics | antibiotic Category of Biology
An antibiotic is a type of antimicrobial substance which is active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity, but antibiotics are not effective against viruses or fungi.
Sometimes, the term antibiotic—literally "opposing life", from the Greek roots ἀντι anti, "against" and βίος bios, "life"—is broadly used to refer to any substance used against microbes, but in the usual medical usage, antibiotics (such as penicillin) are those produced naturally (by one microorganism fighting another), whereas non-antibiotic antibacterials (such as sulfonamides and antiseptics) are fully synthetic. However, both classes have the same effect of killing or preventing the growth of microorganisms, and both are included in antimicrobial chemotherapy. "Antibacterials" include bactericides, bacteriostatics, antibacterial soaps, and chemical disinfectants, whereas antibiotics are an important class of antibacterials used more specifically in medicine and sometimes in livestock feed.