Definition of penicillin
1 : any of several relatively nontoxic antibiotic acids of the general formula C9H11N2O4SR that are produced by molds (genus Penicillium and especially P. notatum or P. chrysogenum) or synthetically and are used especially against gram-positive cocci; also : a mixture of such acids
2 : a salt or ester of a penicillin or a mixture of such salts or esters
Recent Examples of penicillin from the Web
In 1928, Alexander Fleming discovered penicillin, which was arguably the most important medical breakthrough in history.
Alexander Fleming [the biologist who serendipitously discovered penicillin] loved games.
But even after penicillin was discovered in 1947 and used as a treatment for the disease, the men in the Tuskegee study were not offered the antibiotic.
The doctor on call peered into Fair's mouth, diagnosed him with strep throat, and administered a penicillin shot, reducing the swelling.
In the mid-1940s, when penicillin became the standard treatment for syphilis, doctors never provided the men with the lifesaving treatment.
The men that had the disease were never informed or treated for it, even after penicillin became an effective treatment for syphilis.
When the study began, the discovery of penicillin as a cure for syphilis was still 10 years away and the general availability of the drug was 15 years away.
The researchers did find some good news: Various forms of penicillin, the most commonly used antibiotic during pregnancy, and cephalosporins such as Cephalexin were not shown to increase the chances of early pregnancy termination.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'penicillin'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Origin and Etymology of penicillin
New Latin Penicillium
First Known Use: 1929See Words from the same year
PENICILLIN Defined for English Language Learners
Definition of penicillin for English Language Learners
: a medicine that is used to kill harmful bacteria
PENICILLIN Defined for Kids
Definition of penicillin for Students
: an antibiotic that is produced by a mold and is used against disease-causing bacteria
Medical Definition of penicillin
1: a mixture of relatively nontoxic antibiotic acids produced especially by molds of the genus Penicillium (as P. notatum or P. chrysogenum) and having a powerful bacteriostatic effect against various chiefly gram-positive bacteria (as staphylococci, gonococci, pneumococci, hemolytic streptococci, or some meningococci)
2: any of numerous often hygroscopic and unstable amido acids (as penicillin G, penicillin O, and penicillin V) that have a structure in which a four-membered lactam ring shares a nitrogen and a carbon atom with a thiazolidine ring to which it is fused and that are components of the penicillin mixture or are produced biosynthetically by the use of different strains of molds or different media or are synthesized chemically
3: a salt or ester of a penicillin acid or a mixture of such salts or esters
Seen and Heard
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