Antibiotics play major role in today treatment system. Antibiotics are produced by natural way through fermentation or by semi-synthesis or synthesis method.
Antibiotics are classified in many ways e.g. According to their mechanism of action, chemical composition etc.
Aminoglycosides: Aminoglycosides antibiotics contain a basic 6 member carbon ring (amino or gaunidino) to which one or more amino sugar are attached through a glycosidic linkage. Mainly these antibiotics block protein synthesis by combining with bacterial rhizomes. They have broad spectrum activity against gram negative bacteria.
Penicillins: Penicillins are the a-carboxamide derivatives of penicillanic acid. Penicillins are of two type: Natural and Semi-synthetic. Penicillins prevent the formation of bacterial cell wall by interfering with the synthesis of N-acteylmuramic acid, mucopeptides and teichoic acids. Few examples of Penicillins are Penicillin, Ampicillin, Amoxicillin, and Penicillin G etc. Penicillins are effective mainly against gram positive bacteria. Penicillins are sensitive against beta-lactase enzymes and don’t produce effect.
Cephalosporin: They are derivatives of cephalosporanic acid, which is a close analogue of penicillanic acid. Cephalosporanic acid contains dihydrometathiazine ring. They also kill bacterial by interfering with cell wall synthesis. Examples: Cephalexin, cefazolin, cephapirin etc.
Macrolides: Chemically macrolides are macrocyclic lactones with 12 to 20 carbon atoms in the primary ring. Macrolides block the translocation step in protein synthesis by binding to 50s sub unit of the bacterial rhizomes. Erythromycin is a well known example of Macrolides. Erythromycin is mainly effective against gram positive bacterial infections.
Tetracyclines: Tetracyclines inhibits protein synthesis by binding to 30s ribosomes and preventing t-RNA from combining with m-RNA. Tetracyclines is a group of antibiotics containing octahydronaphthacene skeleton. Examples: Minocycline, methacycline, chlortetracycline etc. Tetracyclines are broad spectrum antibiotics active gainst gram positive and gram negative bacteria, rickettsia and viruses.
Polypeptides: Polypeptides are the antibiotics composed of a number of amino acids joined through peptide linkage and have a cyclic structure. They contain unnatural D-configuration amino acids. These antibiotics are used in many cases for topical applications. Examples: Bacitracin zinc, colistin sulphate, gramicidin etc.
Miscellaneous Antibiotics: Antibiotics in this group vary in chemical composition and mechanism of actions. Some antibiotics are the products of bacteria which have unique biosynthesis pattern. Example: Rifampin, cycloserine, vancomycin, chlorampenicol, clindamycin etc.
Antibiotics are also classified in many ways. One other method of classification of antibiotics is according to their mechanism of action:
- Inhibition of Protein synthesis
- Inhibition of cell wall formation
- Disruption of DNA metabolism
- Alteration in cellular membrane function