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Antibiotic resistance mechanisms reported in Gram-negative bacteria are causing a worldwide health problem. The continuous dissemination of 'multidrug-resistant' (MDR) bacteria drastically reduces the efficacy of our antibiotic 'arsenal' and consequently increases the frequency of therapeutic failure. In MDR bacteria, the overexpression of efflux pumps that(More)
BACKGROUND Membrane permeability is the first step involved in resistance of bacteria to an antibiotic. The number and activity of efflux pumps and outer membrane proteins that constitute porins play major roles in the definition of intrinsic resistance in Gram-negative bacteria that is altered under antibiotic exposure. METHODOLOGY/PRINCIPAL FINDINGS(More)
The present study assessed the antimicrobial activities of various natural products belonging to the terpenoids, alkaloids and phenolics against a collection of Gram-negative multidrug-resistant (MDR) bacteria. The results demonstrated that most of the compounds were extruded by bacterial efflux pumps. In the presence of the efflux pump inhibitor(More)
Chemoresistance presents a general health problem concerning the therapy of infectious disease and cancer. In this context, the worldwide dissemination of "multidrugresistant" (MDR) pathogens has severely reduced the efficacy of our antimicrobial weapons and dramatically increased the frequency of therapeutic failure. Because MDR bacterial infections(More)
Seven hybridoma clones, producing antibodies directed against the beta 2-subunit of Escherichia coli tryptophan synthase, have been obtained from mouse cells. To test whether the corresponding monoclonal antibodies recognize different epitopes on beta 2, an ELISA double antibody binding system has been developed and is reported here. The antigen is first(More)
After several decades of continuously successful antibiotic therapy against bacterial infections, we are now facing a worrying prospect: the accelerated evolution of antibiotic resistance to important human pathogens and the scarcity of new anti-infective drug families under development. Efflux is a general mechanism responsible for bacterial resistance to(More)
Multidrug-resistant Enterobacter aerogenes strains are increasingly isolated in Europe and especially in France. Treatment leads to imipenem resistance, because of a lack of porin. We studied the evolution of resistance in 29 strains isolated from four patients during their clinical course. These strains belonged to the prevalent epidemiological type(More)
A strain of Escherichia coli, selected on the basis of its resistance to colicin N, reveals distinct structural and functional alterations in unspecific OmpF porin. A single mutation [Gly-119-->Asp (G119D)] was identified in the internal loop L3 that contributes critically to the formation of the construction inside the lumen of the pore. X-ray structure(More)
In Gram-negative bacteria, the envelope is a sophisticated barrier protecting the cell against external toxic compounds. Membrane transporters, e.g., porins or efflux pumps, are main filters regulating the internal accumulation of various hydrophilic molecules. Regarding bacterial susceptibility towards antibacterial agents, membrane permeability is part of(More)
Cerulenin, a drug which specifically blocks lipid synthesis, prevented both the trimerization of OmpF monomers and their assembly into the outer membrane of Escherichia coli B cells. A monoclonal antibody directed against a surface-exposed epitope of the trimer was used to probe the assembly of OmpF in the presence or absence of the drug. An inhibition(More)