Polymyxin antibiotics

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. 

Polymyxin B. Polymyxin antibiotics are cationic compounds that are attracted to negatively charged phospholipids in the bacterial cell membrane. These drugs penetrate and disrupt the architecture and integrity of the surface membrane. Essentially, polymyxins act as detergents that break apart the phospholipid bilayer, which creates gaps in the bacterial cell wall, leading to the subsequent destruction of the bacteria.31... 

In the antibiotic field, Vogler and Studer have reviewed the chemistry of the polymyxin antibiotics. Studer, Lergier and-Vogler l reported the synthesis of Circulin A, and Ohno and coworkers° synthesized tyrocidin A. 

Polymyxin. Antibiotic complex produced by Bacillus polymyxa Brownlee, Jones, Biochem. J. 43, XXV... 

Fig. 5. Polymyxin antibiotics general structure. Z)y45=diaminobutyric acid Le = leucine r/ir=threonine. 7=polymyxin-B, 7/=polymyxin-E...

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