Temocillin is a β-lactamase resistant carboxypenicillin. introduced by Beecham, marketed by Eumedica Pharmaceuticals as primarily for the treatment of multiresistant Gram negative bacteria, such as Salmonella and Escherichia coli. It is not active against Gram positive bacteria or bacteria with altered penicillin-binding proteins. The common dosage is 2g intravenously every 12 hours.

The term "antibiotic" was coined by Selman Waksman in 1942 to describe any substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution. This definition excluded substances that kill bacteria but are not produced by microorganisms (such as gastric juices and hydrogen peroxide). It also excluded synthetic antibacterial compounds such as the sulfonamides. Many antibacterial compounds are relatively small molecules with a molecular weight of less than 2000 atomic mass units.

With advances in medicinal chemistry, most of today's antibacterials chemically are semisynthetic modifications of various natural compounds. These include, for example, the beta-lactam antibacterials, which include the penicillins (produced by fungi in the genus 'Penicillium'), the cephalosporins, and the carbapenems. Compounds that are still isolated from living organisms are the aminoglycosides, whereas other antibacterials—for example, the sulfonamides, the quinolones, and the oxazolidinones—are produced solely by chemical synthesis.

Formal Chemical Name (IUPAC)