Colistin is a polymyxin antibiotic, it is a mixture of cyclic polypeptides colistin A and B. Colistin is effective against most Gram-negative bacilli and is used as a polypeptide antibiotic.
Colistin sulfate is used to permeabilize bacterial cell membranes and to study mannose-resistant haemagglutination and antibiotic resistance in certain organisms such as A. baumannii. It has been used to study hephrotoxicity in the rat kidney, and MICs, time-kill kinetics, and postantibiotic effect (PAE) against Pseudomonas aeruginosa.
Mode of Action: Binds to lipids on the cell cytoplasmic membrane of Gram-negative bacteria and disrupts the cell wall integrity. Antimicrobial spectrum: Gram-negative bacteria. It is proposed that renal reabsorption of colistin may involve organic cation transporters and peptide transporters and that the process is sensitive to pH.