The effect of lipopolysaccharide on lipid bilayer permeability of beta-lactam antibiotics.

The lipid-bilayer permeability of cephalosporins was extensively suppressed by addition of lipopolysaccharide to liposomal membrane in proportion to the hydrophobicity of the drugs. This suggests that the polysaccharide chain layer contributes to the barrier function. The importance of the polysaccharide chain in the barrier function was also supported by the fact that the permeability to Rd-type lipopolysaccharide-containing liposomes showed essentially the same dependency on the hydrophobicity of the cephalosporins as that of the lipopolysaccharide-free liposomes. In this case the permeability of the cephalosporins was proportional to their hydrophobicity. Similar lipopolysaccharide effect was also observed in the permeation of penicillins.