The contribution of porins to enterobacterial drug resistance.

In Enterobacteriaceae, susceptibility to cephalosporins and carbapenems is often associated with membrane and enzymatic barrier resistance. For about 20 years, a large number of Klebsiella pneumoniae, Escherichia coli and Enterobacter cloacae presenting ß-lactam resistance have been isolated from medical clinics. In addition, some of the resistant isolates exhibited alterations in the outer membrane porin OmpC-OmpF orthologues, resulting in the complete absence of gene expression, replacement by another porin or mutations affecting channel properties.

Budmunchiamines as a Potential Adjuvant for Rejuvenating Phenicol Activities towards -Resistant Strains.

The continuous emergence of bacterial resistance alters the activities of different antibiotic families and requires appropriate strategies to solve therapeutic impasses. Medicinal plants are an attractive source for researching alternative and original therapeutic molecules. In this study, the fractionation of natural extracts from and the determination of antibacterial activities are associated with molecular networking and tandem mass spectrometry (MS/MS) data used to characterize active molecule(s).

Contribution of efflux and mutations in fluoroquinolone susceptibility in MDR enterobacterial isolates: a quantitative and molecular study.

Objectives: The emergence of MDR strains is a public health problem in the management of associated infections. Several resistance mechanisms are present, and antibiotic efflux is often found at the same time as enzyme resistance and/or target mutations. However, in the laboratory routinely, only the latter two are identified and the prevalence of antibiotic expulsion is underestimated, causing a misinterpretation of the bacterial resistance phenotype.

Rejuvenating the Activity of Usual Antibiotics on Resistant Gram-Negative Bacteria: Recent Issues and Perspectives.

Antibiotic resistance continues to evolve and spread beyond all boundaries, resulting in an increase in morbidity and mortality for non-curable infectious diseases. Due to the failure of conventional antimicrobial therapy and the lack of introduction of a novel class of antibiotics, novel strategies have recently emerged to combat these multidrug-resistant infectious microorganisms. In this review, we highlight the development of effective antibiotic combinations and of antibiotics with non-antibiotic activity-enhancing compounds to address the widespread emergence of antibiotic-resistant strains.

A framework for dissecting affinities of multidrug efflux transporter AcrB to fluoroquinolones.

Sufficient concentration of antibiotics close to their target is key for antimicrobial action. Among the tools exploited by bacteria to reduce the internal concentration of antibiotics, multidrug efflux pumps stand out for their ability to capture and expel many unrelated compounds out of the cell. Determining the specificities and efflux efficiency of these pumps towards their substrates would provide quantitative insights into the development of antibacterial strategies.

Cephalosporin translocation across enterobacterial OmpF and OmpC channels, a filter across the outer membrane.

Gram-negative porins are the main entry for small hydrophilic molecules. We studied translocation of structurally related cephalosporins, ceftazidime (CAZ), cefotaxime (CTX) and cefepime (FEP). CAZ is highly active on E.

An Outer Membrane Vesicle-Based Permeation Assay (OMPA) for Assessing Bacterial Bioavailability.

When searching for new antibiotics against Gram-negative bacterial infections, a better understanding of the permeability across the cell envelope and tools to discriminate high from low bacterial bioavailability compounds are urgently needed. Inspired by the phospholipid vesicle-based permeation assay (PVPA), which is designed to predict non-facilitated permeation across phospholipid membranes, outer membrane vesicles (OMVs) of Escherichia coli either enriched or deficient of porins are employed to coat filter supports for predicting drug uptake across the complex cell envelope. OMVs and the obtained in vitro model are structurally and functionally characterized using cryo-TEM, SEM, CLSM, SAXS, and light scattering techniques.

Tolerance engineering in Deinococcus geothermalis by heterologous efflux pumps.

Producing industrially significant compounds with more environmentally friendly represents a challenging task. The large-scale production of an exogenous molecule in a host microfactory can quickly cause toxic effects, forcing the cell to inhibit production to survive. The key point to counter these toxic effects is to promote a gain of tolerance in the host, for instance, by inducing a constant flux of the neo-synthetized compound out of the producing cells.

An Intertwined Network of Regulation Controls Membrane Permeability Including Drug Influx and Efflux in Enterobacteriaceae.

The transport of small molecules across membranes is a pivotal step for controlling the drug concentration into the bacterial cell and it efficiently contributes to the antibiotic susceptibility in . Two types of membrane transports, passive and active, usually represented by porins and efflux pumps, are involved in this process. Importantly, the expression of these transporters and channels are modulated by an armamentarium of tangled regulatory systems.

The challenge of intracellular antibiotic accumulation, a function of fluoroquinolone influx versus bacterial efflux.

With the spreading of antibiotic resistance, the translocation of antibiotics through bacterial envelopes is crucial for their antibacterial activity. In Gram-negative bacteria, the interplay between membrane permeability and drug efflux pumps must be investigated as a whole. Here, we quantified the intracellular accumulation of a series of fluoroquinolones in population and in individual cells of Escherichia coli according to the expression of the AcrB efflux transporter.

Porins and small-molecule translocation across the outer membrane of Gram-negative bacteria.

Gram-negative bacteria and their complex cell envelope, which comprises an outer membrane and an inner membrane, are an important and attractive system for studying the translocation of small molecules across biological membranes. In the outer membrane of Enterobacteriaceae, trimeric porins control the cellular uptake of small molecules, including nutrients and antibacterial agents. The relatively slow porin-mediated passive uptake across the outer membrane and active efflux via efflux pumps in the inner membrane creates a permeability barrier.

Mechanistic aspects of maltotriose-conjugate translocation to the Gram-negative bacteria cytoplasm.

Small molecule accumulation in Gram-negative bacteria is a key challenge to discover novel antibiotics, because of their two membranes and efflux pumps expelling toxic molecules. An approach to overcome this challenge is to hijack uptake pathways so that bacterial transporters shuttle the antibiotic to the cytoplasm. Here, we have characterized maltodextrin-fluorophore conjugates that can pass through both the outer and inner membranes mediated by components of the maltose regulon.

Antibiotics and efflux: combined spectrofluorimetry and mass spectrometry to evaluate the involvement of concentration and efflux activity in antibiotic intracellular accumulation.

Background: In Gram-negative bacteria, passing through the double membrane barrier to reach the inhibitory concentration inside the bacterium is a pivotal step for antibiotic activity. Spectrofluorimetry has been developed to follow fluoroquinolone accumulation inside bacteria using intrinsic bacterial fluorescence as an internal standard. However, adaptation for non-fluorescent antibiotics is needed; quantitative methods based on MS offer the possibility of expanding the detection range obtained by spectrofluorimetry.

Spectrofluorimetric quantification of antibiotic drug concentration in bacterial cells for the characterization of translocation across bacterial membranes.

The efficacy of antibacterial molecules depends on their capacity to reach inhibitory concentrations in the vicinity of their target. This is particularly challenging for drugs directed against Gram-negative bacteria, which have a complex envelope comprising two membranes and efflux pumps. Precise determination of the bacterial drug content is an essential prerequisite for drug development.

Fluorescence enlightens RND pump activity and the intrabacterial concentration of antibiotics.

To understand antibiotic resistance in Gram-negative bacteria, a key point is to investigate antibiotic accumulation, which is defined by influx and efflux. Several methods exist to evaluate membrane permeability and efflux pump activity, but they present disadvantages and limitations. An optimized spectrofluorimetric method using intrinsic tryptophan fluorescence as an internal standard, as well as a complementary microfluorimetric assay following time-course accumulation in intact individual cells, have been developed.

Fluoroquinolone structure and translocation flux across bacterial membrane.

Bacterial multidrug resistance is a worrying health issue. In Gram-negative antibacterial research, the challenge is to define the antibiotic permeation across the membranes. Passing through the membrane barrier to reach the inhibitory concentration inside the bacterium is a pivotal step for antibacterial molecules.

In-vivo loss of carbapenem resistance by extensively drug-resistant Klebsiella pneumoniae during treatment via porin expression modification.

Klebsiella pneumoniae, an Enterobacteriaceae that mostly causes hospital-acquired infections, belongs to the recently published WHO's list of antibiotic-resistant pathogens that pose the greatest threat to human health. Indeed, K. pneumoniae is the enterobacterial species most concerned by both resistance to extended-spectrum cephalosporins, due to extended-spectrum β-lactamase (ESBL) production, and resistance to carbapenems, i.

Microspectrofluorimetry to dissect the permeation of ceftazidime in Gram-negative bacteria.

A main challenge in chemotherapy is to determine the in cellulo parameters modulating the drug concentration required for therapeutic action. It is absolutely urgent to understand membrane permeation and intracellular concentration of antibiotics in clinical isolates: passing the membrane barrier to reach the threshold concentration inside the bacterial periplasm or cytoplasm is the pivotal step of antibacterial activity. Ceftazidime (CAZ) is a key molecule of the combination therapy for treating resistant bacteria.

New amphiphilic neamine conjugates bearing a metal binding motif active against MDR E. aerogenes Gram-negative bacteria.

Structure of bacterial envelope is one of the major factors contributing to Gram negative bacterial resistance. To develop new agents that target the bacterial membranes, we synthesized, by analogy with our previous peptide conjugates, new amphiphilic 3',4',6-trinaphthylmethylene neamines functionalized at position 5 through a short spacer by a chelating group, tris(2-pyridylmethyl)amine (TPA) and di-(picolyl)amine (DPA) and tetraazacyclotetradecane (Cyclam). ESI mass spectrometry analyses showed that neither Zn(II)(NeaDPA) nor Cu(II)(NeaCyclam) were stable in the Mueller Hinton (MH) medium used for antibacterial assays.

A day in the life of microcystis aeruginosa strain PCC 7806 as revealed by a transcriptomic analysis.

The cyanobacterium, Microcystis aeruginosa, is able to proliferate in a wide range of freshwater ecosystems and to produce many secondary metabolites that are a threat to human and animal health. The dynamic of this production and more globally the metabolism of this species is still poorly known. A DNA microarray based on the genome of M.