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β-Lactam antibiotics are indicated for the prevention and treatment of bacterial infections caused by susceptible organisms. At first, β-lactam antibiotics were mainly active only against gram-positive bacteria, yet the recent development of broad-spectrum β-lactam antibiotics active against various gram-negative organisms has increased their usefulness.
A lactam is a cyclic amide, and beta-lactams are named so because the nitrogen atom is attached to the β-carbon atom relative to the carbonyl. The simplest β-lactam possible is 2-azetidinone. β-lactams are significant structural units of medicines as manifested in many β-lactam antibiotics. [2]
Beta-lactam ring in red. Escherichia coli bacteria on the right are sensitive to two beta-lactam antibiotics, and do not grow in the semi-circular regions surrounding antibiotics. E. coli bacteria on the left are resistant to beta-lactam antibiotics, and grow next to one antibiotic (bottom) and are less inhibited by another antibiotic (top).
The β-lactam core structures. (A) A penam.(B) A carbapenam.(C) An oxapenam.(D) A penem.(E) A carbapenem.(F) A monobactam.(G) A cephem.(H) A carbacephem.(I) An oxacephem. This is a list of common β-lactam antibiotics—both administered drugs and those not in clinical use—organized by structural class.
Lactamization is most efficient in this way if the product is a γ-lactam. For example, Fmoc-Dab(Mtt)-OH, although its side-chain amine is sterically protected by extremely bulky 4-Methyltrityl (Mtt) group, the amine can still intramolecularly couple with the carboxylic acid to form a γ-lactam.
Clavulanic acid strongly inhibits β-lactamase in bacteria, which is associated with its antibiotic properties. β-Lactam antibiotics generally have a common feature which is the 3-carbon and 1-nitrogen ring (β-lactam ring) that is highly reactive. [8]
Nafcillin sodium is a narrow-spectrum, [1] second-generation beta-lactam antibiotic [2] of the penicillin class. As a beta-lactamase-resistant penicillin, it is used to treat infections caused by Gram-positive bacteria, in particular, species of staphylococci that are resistant to other penicillins.
Dicloxacillin is a narrow-spectrum β-lactam antibiotic of the penicillin class. [1] It is used to treat infections caused by susceptible (non-resistant) Gram-positive bacteria. [1] It is active against beta-lactamase-producing organisms such as Staphylococcus aureus, which would otherwise be resistant to most penicillins.