Resistance to Antibacterial Agents Acting on Cell Membranes

Influence of phenols on growth and membrane permeability of free and immobilized Escherichia coli

“…On the basis of this study, it can be expected that protection of cells from phenolic solvents generally exists in all environments in which forms of immobilization or cell adhesion (including biofilms) are present. This is especially important considering that development of resistance to phenols is seldom reported and then is based on exclusion of the antimicrobial compound by an impermeable cell wall or outer membrane (7,9). With regard to the observations presented here, it can also be supposed that, besides phenols, other membrane-active compounds at sublethal concentrations are less inhibitory to immobilized microorganisms than they are to free microorganisms.…”

Alterations in Outer Membrane Permeability

“…In the absence of such chelators, however, the combination of negative charge and divalent cation cross-bridging of LPS provides gram-negative cells with many of their more important properties, including resistance to hy drophobic antibiotics, bile salts, detergents, proteases, lipases, and lysozyme (74,98,102,117,119). The outer membrane also contains a small number of so-called "major" proteins present in high copy number (10 5 copies per cell) (102).…”

“…The self-promoted pathway has been pos tulated for the uptake of polycationic antibiotics, like polymyxins and amino glycosides, across the outer membrane of P. aeruginosa (70,74,75). It involves the displacement of divalent cations from LPS by these polycations, thus destroying the LPS cross-bridging and destabilizing the outer membrane (74,75).…”

“…The self-promoted pathway has been pos tulated for the uptake of polycationic antibiotics, like polymyxins and amino glycosides, across the outer membrane of P. aeruginosa (70,74,75). It involves the displacement of divalent cations from LPS by these polycations, thus destroying the LPS cross-bridging and destabilizing the outer membrane (74,75). Because this can result in enhancement of uptake of lysozyme, �-lactams (75), and hydrophobic fluorescent dyes (l00) across the outer membrane, we have proposed that such interactions promote the uptake of the interacting polycationic antibiotic itself.…”

“…For this effect. and for a wide range of outer membrane permeabilization events mediated by po lymyxin ( (70,74,113). We have proposed that the interal�tion of aminoglycosides with P. aeruginosa outer membranes at this site is part of an uptake mechanism (i.e.…”