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.
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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.