Susceptibility of porin- and lipopolysaccharide-deficient strains of Escherichia coli to some antiseptics and disinfectants.

The sensitivities of some outer membrane protein (Omp) and/or lipopolysaccharide (LPS)-defective mutants of Escherichia coli to chlorhexidine and some quaternary ammonium compounds (QACs) were examined. Wild-type strains, with no defect in Omp or LPS were the most resistant to QACs, whereas LPS-deficient strains were the most sensitive. As expected, QAC resistance could not be related to the presence or absence of any specific porin(s). Chlorhexidine was highly active against all strains, inhibitory concentrations lying within the narrow range of 1 and 2 mg l-1.