Colistin Sulfate
Colistin (Polymyxin E) is polymyxin antibiotic produced by culture of Bacillus polymyxa var colistinus. It is effective primarily against gram-negative microorganisms such as E-coil and Salmonella. Colistin is bactericidal and it causes disorganisation of the bacterial cell membrane with leakage of intracellular materials and inhibits bacterial oxidative metabolism. Gram-positive bacteria are naturally resistant to colistin. However, acquired resistance of gram-negative enteric bacteria to colistin is uncommon.
In the target species, colistin sulfate is very poorly absorbed after oral administration. Plasma concentrations after oral administration are generally undetectable. Orally administered colistin is excreted in the faeces.