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Antibiotic Definition

: a substance able to inhibit or kill microorganisms specifically

: an antibacterial substance (such as penicillin, cephalosporin, and ciprofloxacin) that is used to treat or prevent infections by killing or inhibiting the growth of bacteria in or on the body, that is administered orally, topically, or by injection, and that is isolated from cultures of certain microorganisms (such as fungi) or is of semi-synthetic or synthetic origin Symptoms of campylobacteriosis include muscle aches, fever, cramps and diarrhea leading to gastrointestinal illness, which can be treated with antibiotics. — Chicago Daily Herald

Another way to produce new variants of established antibiotics is to use genetic engineering to alter the biochemical pathways of the microbes that produce them. — New Scientist

Experts agree that by spiking animal feed with antibiotics, conventional farmers are speeding the emergence of drug-resistant bacteria. — Geoffrey Cowley

Note: While antibiotics are effective mainly against bacteria, they are sometimes used to treat protozoal infections. Some consider antibiotics to include only those derived fully or partly from microorganisms and exclude synthetic forms from this class of drugs.

antibiotic adjective

Definition of antibiotic (Entry 2 of 2) 1 : tending to prevent, inhibit, or destroy life 2 : of or relating to antibiotics or to antibiosis antibiotic drugs Other Words from antibiotic More Example Sentences Learn More about antibiotic

Other Words from antibiotic

Adjective antibiotically \ ˌan-​tē-​bī-​ˈä-​ti-​k(ə-​)lē , ˌan-​ˌtī-​ ; -​bē-​ˈä-​ \ adverb

Examples of antibiotic in a Sentence

Recent Examples on the Web: Noun Infection symptoms for humans, beyond diarrhea, include fever and stomach cramps two to five days after exposure, according to the CDC, which says most people recover in about a week without antibiotics. —,

“Thirty people have reported infections as of Tuesday, according to the Centers for Disease Control and Prevention, which says the outbreak seems to stem mostly from dogs purchased at pet shops. About 70 percent of those sickened who were interviewed reported contact with a pet store puppy.,” 19 Dec. 2019

The strain isolated in this outbreak is resistant to commonly recommended, first-line antibiotics. — Audrey Mcnamara, CBS News, “Pet store puppies linked to outbreak of infections in humans, CDC says,” 18 Dec. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word ‘antibiotic.’ Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback. See More

First Known Use of antibiotic


1943, in the meaning defined above


1891, in the meaning defined at sense 1

History and Etymology for antibiotic


derivative of antibiotic entry 2

Note: Noun use of the adjective antibiotic probably began in the early 1940’s, preceded by the frequent collocation antibiotic substance, but was not common before Selman Waksman‘s paper “What Is an Antibiotic or an Antibiotic Substance?” (Mycologia, vol. 39, no. 5 [September-October, 1947]). Waksman has been credited with coining antibiotic, though he does not claim to have done so, and in fact gives an account of the earlier history of the word in this article.


borrowed from French antibiotique, derivative of antibiose antibiosis (after symbiose symbiosis : symbiotique symbiotic)

Note: See note at antibiosis.

Source- Merriam-Webster

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