Comments
Colistin was isolated from filtrates of Bacillus colistinus and is identical to Polymyxin E (mainly E1 and E2). It is a cyclic pentapeptide with a pentapeptide side chain. Colistin is active only against proliferating and non-proliferating gram negative organism. It interacts with phospholipids of the cytoplasmic membrane of bacteria and permeabilizes them. The efflux of essential components explains its bactericidal activity on non-proliferating organisms. The bactericidal activity will be reduced by divalent ions (Fe2\+, Mn2\+, Ca2\+, Mg2\+), unsaturated fatty acids and polyphosphates.Stability: A high stability is observed at pH values between 2 and 6. At pH values above 6.0, a slow inactiviation occurs (pH 9, 24 hours, 50 % inactivation). At pH 2, only 1 % will be inactivated within 24 hours. Solutions with a concentration of 10 mg/ml are stable at \+4°C for more than 10 - 14 days.
