Cationic Antisepetices

Cationic Antisepetices

	Cationic Antisepetices - These compounds contain strong basic groups attached to a large nonpolar molecule. Chlorohexidine is one of the most widely used cationic antiseptics. It has low toxicily and irritancy, and is effective against a wide range of bacteria. It acts mainly by inhibiting ATPase of the cytoplasmic membrane, and by inhibiting the net uptake of potassium ions by the cells.
Polypeptide antibiotics have only a minor place in medicine. The antibacterial action is primarily due to their ability to bind to the cytoplasmic membrane. Two groups of polypeptide antibiotics studied in detail are the cyclic decapeptides and the polymixins. Cyclic decapeptides contain 10 amino acid residues, including some D form, arranged in a ring. T4ey contain one, or sometimes two, free amino groups. They show greater activity against gram positive than against gram negative bacteria. Examples of cyclic decapeptides are tyrocidins and gramicidin S. Tyrocidins promote leakage of cytoplasmic solutes by permitting entry into the cell of ions normally excluded. Gramicidin S also acts in a similar manner.
The polymixins have a smaller polypeptide ring, to which is attached a polypeptide chain ending in a branched 8 or 9C fatty acid residue. The five diaminobutyric acid (DAB) units in polymixins provide the five free amino groups. The antibacterial activity of polymixins is mainly against gram negative bacteria. They act by increasing the permeability of the ceil membrane and releasing solutes.

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