Colistin polymyxin

The polymyxins are a group of basic peptides active against gram-negative bacteria and include polymyxin and polymyxin E (colistin). Polymyxins act like cationic detergents. They attach to and disrupt bacterial cell membranes. They also bind and inactivate endotoxin. Gram-positive organisms, proteus, and neisseria are resistant. 

Polymyxin B and colistin (polymyxin E) (Fig. 3.9) are the least toxic of the five polymyxin antibiotics designated alphabetically A-E. Both polymyxin B and colistin are complex polypeptide compounds with specialized activity against gram-negative organisms but they are both nephrotoxic. Topical application and oral administration are more commonly used routes. Polymyxin B is used widely in ointments for topical applications and may be effective in case of mastitis, but it seldom is administered parenterally because of the possibility of renal toxicity. 

Fig. 3.9 Chemical structures of colistin, polymyxin, rifaximin, rifamycin SV, novobiocin, and tiamulin.

The cytoplasmic membrane inside the cell wall is the site of most of the microbial cell s biochemical activity. Drugs that interfere with its function include polyenes (nystatin, amphotericin), azoles (fluconazole, itraconazole, miconazole), polym5odns (colistin, polymyxin B). 

Organism Amphomycin Bacitracin Tyrothricin Gramicidin Tyrocidine Gramicidin S Colistin Polymyxin B Viomycin... 

Simultaneous colistin, polymyxin C, polymyxin D, polymyxin E, polymyxin M, polymyxin S, polymyxin T... 

Kitamura-Matsunaga, H. Kimura, Y. Araki, T. Izumiya, N. A sodium-containing polymyxin derived from polymyxin-complex during chromatography. J.Antibiot.(Tokyo), 1984, 37, 1605-1610 [for colistin, polymyxin E anal3d ical preparative]... 

Colistin (polymyxin E) is available as colistin sulfate for oral use and as colistimethate sodium for parenteral administration (not recommended). The antimicrobial activities of polymyxin B and colistin are restricted to gram-negative bacteria. 

Since Hydrogenomonas strain H16 and many other strains of hydrogen bacteria are not affected by penicillin or its derivatives, the well-known penicillin technique for the selection of auxotrophic mutants cannot be applied. However, colistine (= polymyxine B) proved to be an effective agent which kills only growing cells leaving non-growing cells unimpaired (Schlegel et al, 1965). 

The polypeptides include bacitracin A, colistin (polymyxin E), novobiocin, and polymyxin B. Bacitracin is a complex mixture of branched, cyclic decapeptides produced by Bacillus subtilise, which was first isolated in 1945. The polymyxins, discovered in 1947, are synthesized by various strains of Bacillus polymyxa. Colistin (polymyxin E) comprises a family of polymyxins and was known as colimycin when first isolated from a broth of Bacillus polymyxa var. colistinus in 1951. The polymyxins are cationic detergents. Novobiocin, first reported in 1955 as streptonivicin, is produced by the actinomycete Streptomyces niveus. 

Polypeptides Bacitracin, Colistimethate sodium, Colistin, Polymyxin B, Tekoplanin, Vancomycin... 

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