[CAS NO. 1264-72-8]  Colistin Sulfate

Colistin (2 μg/mL) is active against most strains of Escherichia coli and P. aeruginosa, and all species of Enterobacter, Salmonella, Shigella, Pasteurella, Brucella, and Bordetella. Proteus, Serratia, Providencia. Colistin inhibits 225 strains of P.aeruginosa with MIC90 and MIC50 of 6.3 μg/mL and 1.6μg/mL, respectively. Colistin sulfate is approved only for topical and oral use because of its toxicity. Colistin sulfate is administered orally (tablets or syrup) for bowel decontamination and topically as a powder for the treatment of bacterial skin infections. Colistin interacts with the bacterial membrane through electrostatic interactions between the cationic polypeptide (colistin) and anionic lipopolysaccharide (LPS) molecules in the outer membrane of the gram-negative bacteria, leading to derangement of the cell membrane. Colistin displaces magnesium (Mg) and calcium (Ca), which normally stabilize the LPS molecules, from the negatively charged LPS, leading to a local disturbance of the outer membrane. Colistin has also potent anti-endotoxin activity. Colistin sulfate produces a strong postantibiotic effects against Acinetobacter baumannii ranging from 2.5 hours to 7.0 hours in a concentration-dependent manner.