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Polymixins

 

Mode of action:

 

Inhibition of cell membrane function. Disrupt the structure of cell membrane phospholipids and increase cell permeability by a detergent-like action, causing cell death.  This binding is competitive with calcium and magnesium. Polymixins have also been shown to neutralize endotoxins.

 

Example:

Polymixin B, colistin (Polymixin E)

 

Source:

Bacillus polymyxa

Spectrum of activity:

Narrow spectrum affecting primarily Gram negative bacteria

 

Effect on bacteria:

Bactericidal

 

Examples of applications in Veterinary Medicine:

Cattle: colibacillosis and salmonellosis in calves, mastitis

Swine: neonatal porcine colibacillosis

Horses: bacterial keratitis or metritis caused by Klebsiella spp.

Dogs and cats: bacterial keratitis, otitis externa, skin infections

 

Miscellaneous:

 

Polymixins are not absorbed from the gastrointestinal tract.  Because of their excessive nephrotoxic nature, other polymixin classes have been discarded.

 

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