| Cyclic polypeptide antibiotic produced by Bacillus polymyxa. Complex mixture of at least 30 components, primarily colistin A and B. Colistin (polymyxin E) is a polymyxin antibiotic produced by certain strains of Bacillus polymyxa var. colistinus. Colistin 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 is a decades-old drug that fell out of favor due to its nephrotoxicity. It remains one of the last-resort antibiotics for multidrug-resistant Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter.[1] New Delhi metallo-beta-Lactamase multidrug-resistant Enterobacteriaceae have also shown susceptibility to Colistin.[2] Colistin is polycationic and has both hydrophilic and lipophilic moieties. These poly-cationic regions interact with the bacterial outer membrane, by displacing bacterial counter ions in the lipopolysaccharide. Hydrophobic/hydrophillic regions interact with the cytoplasmic membrane just like a detergent, solubilizing the membrane in an aqueous environment. This effect is bactericidal even in an isosmolaric environment. Resistance to colistin is currently rare, but is described. At present there is no agreement about how to look for colistin resistance. The Societe Francaise de Microbiologie uses a cut off of 2 mg/l, whereas the British Society for Antimicrobial Chemotherapy sets a cutoff of 4 mg/l or less as sensitive, and 8 mg/ml or more as resistant. There are not currently any US standards for measuring colistin sensitivity. Exceptional (inherently colistin resistant) Gram-negative bacteria: Brucella Burkholderia cepacia Chryseobacterium indologenes Edwardsiella Elizabethkingia meningoseptica Francisella tularensis spp. Gram-negative cocci Helicobacter pylori Moraxella catarrhalis Neisseria gonorrheae and Neisseria meningitidis Proteus Providencia Serratia Some strains of Stenotrophomonas maltophilia[18] Gram-negative organisms with variable resistance to colistin: Aeromonas Vibrio Prevotella Fusobacterium Synonyms: Polymyxin E. sulfate, Belcomycine, Colomycin CAS No: 1264-72-8 Molecular Formula: x(C53H100N16O13)ₐ + x(C 52H98N16O13)B .xH2 Molecular Weight: 1169.46 Appearance: Supplied as an off-white solid. Purity: ~98% Biological Potency (dry basis): 19600U/mg Melting Point: >202C (dec.) Specific Rotation (c=1, Water): -64.0 to -65 Colistin A: R= (+)-6-methyloctanoyl Colistin B: R= 6-methylheptanoyl Solubility: Water (Sparingly) Method for Determining Identity: Proton NMR (D2O)Spectroscopic and Mass Spectrometric Analysis TLC Conditions: C18, Water: Methanol: Acetic Acid, 7: 2: 1, Visualized with KMnO4, Single spot, Rf=0.35 Elemental Analysis: Calculated: %C: 54.43, %H: 8.62, %N: 19.16 Storage and Stability: May be stored at RT for short-term only. Long-term storage is recommended at -20C. For maximum recovery of product, centrifuge the original vial prior to removing the cap. Important Note: This product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications without the expressed written authorization of United States Biological. Toxicity and Hazards: All products should be handled by qualified personnel only, trained in laboratory procedures. |
