NCIt definition : The sulfate salt form of polymyxin B1, a polypeptide obtained from Bacillus polymyxa
strains with antimicrobial activity. Polymyxin B1 exerts its antimicrobial effect
through its cationic detergent action on cell membranes. Specifically, this antibiotic
binds to the negatively charged site in the lipopolysaccharide layer of the bacterial
cell membrane via electrostatic affinity with the positively charged amino groups
in the cyclic peptide portion. Subsequently, the fatty acid portion of polymyxin B1
dissolves in the hydrophobic region of the bacterial cell membrane. This results in
an alteration in cell membrane structure, disruption of cell wall integrity and an
increase in permeability for water and molecules. This will eventually lead to bacterial
cell death.;
Semantic type(s)