Small molecule MarR modulators potentiate metronidazole antibiotic activity in aerobic E. coli by inducing activation by the nitroreductase NfsA.

Antibiotic-resistant Enterobacterales pose a major threat to healthcare systems worldwide, necessitating the development of novel strategies to fight such hard-to-kill bacteria. One potential approach is to develop molecules that force bacteria to hyper-activate prodrug antibiotics, thus rendering them more effective. In the present work, we aimed to obtain proof-of-concept data to support that small molecules targeting transcriptional regulators can potentiate the antibiotic activity of the prodrug metronidazole (MTZ) against Escherichia coli under aerobic conditions.

Pyridylpiperazine efflux pump inhibitor boosts in vivo antibiotic efficacy against K. pneumoniae.

Antimicrobial resistance is a global problem, rendering conventional treatments less effective and requiring innovative strategies to combat this growing threat. The tripartite AcrAB-TolC efflux pump is the dominant constitutive system by which Enterobacterales like Escherichia coli and Klebsiella pneumoniae extrude antibiotics. Here, we describe the medicinal chemistry development and drug-like properties of BDM91288, a pyridylpiperazine-based AcrB efflux pump inhibitor.

Characterization of pyridylpiperazine-based efflux pump inhibitors for .

Objectives: In , multidrug efflux pumps belonging to the resistance-nodulation-division (RND) superfamily result in decreased antibiotic susceptibility. Improving the activity of current antibiotics via efflux pump inhibitors (EPIs) represents an attractive alternative approach to control this bacterium. Pyridylpiperazines (PyrPips) are a new class of EPIs that can effectively inhibit the RND efflux pump AcrAB-TolC and boost the activity of several antibiotics.

Optimization of pyridylpiperazine-based inhibitors of the Escherichia coli AcrAB-TolC efflux pump.

Multidrug-resistant Escherichia coli is a continuously growing worldwide public health problem, in which the well-known AcrAB-TolC tripartite RND efflux pump is a critical driver. We have previously described pyridylpiperazines as a novel class of allosteric inhibitors of E. coli AcrB which bind to a unique site in the protein transmembrane domain, allowing for the potentiation of antibiotic activity.

Pyridylpiperazine-based allosteric inhibitors of RND-type multidrug efflux pumps.

Efflux transporters of the RND family confer resistance to multiple antibiotics in Gram-negative bacteria. Here, we identify and chemically optimize pyridylpiperazine-based compounds that potentiate antibiotic activity in E. coli through inhibition of its primary RND transporter, AcrAB-TolC.

Adherent-Invasive and Non-Invasive Isolates Differ in Their Effects on Lifespan.

The adherent-invasive (AIEC) pathotype has been implicated in the pathogenesis of inflammatory bowel diseases in general and in Crohn's disease (CD) in particular. AIEC strains are primarily characterized by their ability to adhere to and invade intestinal epithelial cells. However, the genetic and phenotypic features of AIEC isolates vary greatly as a function of the strain's clonality, host factors, and the gut microenvironment.

Interplay between Yersinia pestis and its flea vector in lipoate metabolism.

To thrive, vector-borne pathogens must survive in the vector's gut. How these pathogens successfully exploit this environment in time and space has not been extensively characterized. Using Yersinia pestis (the plague bacillus) and its flea vector, we developed a bioluminescence-based approach and employed it to investigate the mechanisms of pathogenesis at an unprecedented level of detail.

A refined model of how Yersinia pestis produces a transmissible infection in its flea vector.

In flea-borne plague, blockage of the flea's foregut by Yersinia pestis hastens transmission to the mammalian host. Based on microscopy observations, we first suggest that flea blockage results from primary infection of the foregut and not from midgut colonization. In this model, flea infection is characterized by the recurrent production of a mass that fills the lumen of the proventriculus and encompasses a large number of Y.

Nutrient depletion may trigger the Yersinia pestis OmpR-EnvZ regulatory system to promote flea-borne plague transmission.

The flea's lumen gut is a poorly documented environment where the agent of flea-borne plague, Yersinia pestis, must replicate to produce a transmissible infection. Here, we report that both the acidic pH and osmolarity of the lumen's contents display simple harmonic oscillations with different periods. Since an acidic pH and osmolarity are two of three known stimuli of the OmpR-EnvZ two-component system in bacteria, we investigated the role and function of this Y.

Pyrrolomycins Are Potent Natural Protonophores.

The escalating burden of antibiotic drug resistance necessitates research into novel classes of antibiotics and their mechanism of action. Pyrrolomycins are a family of potent natural product antibiotics with nanomolar activity against Gram-positive bacteria, yet with an elusive mechanism of action. In this work, we dissect the apparent Gram-positive specific activity of pyrrolomycins and show that Gram-negative bacteria are equally sensitive to pyrrolomycins when drug efflux transporters are removed and that albumin in medium plays a large role in pyrrolomycin activity.

Functional and structural analysis of HicA3-HicB3, a novel toxin-antitoxin system of Yersinia pestis.

The mechanisms involved in the virulence of Yersinia pestis, the plague pathogen, are not fully understood. In previous research, we found that a Y. pestis mutant lacking the HicB3 (YPO3369) putative orphan antitoxin was attenuated for virulence in a murine model of bubonic plague.

Genome evolution and plasticity of Serratia marcescens, an important multidrug-resistant nosocomial pathogen.

Serratia marcescens is an important nosocomial pathogen that can cause an array of infections, most notably of the urinary tract and bloodstream. Naturally, it is found in many environmental niches, and is capable of infecting plants and animals. The emergence and spread of multidrug-resistant strains producing extended-spectrum or metallo beta-lactamases now pose a threat to public health worldwide.

Yersinia pestis requires the 2-component regulatory system OmpR-EnvZ to resist innate immunity during the early and late stages of plague.

Plague is transmitted by fleas or contaminated aerosols. To successfully produce disease, the causal agent (Yersinia pestis) must rapidly sense and respond to rapid variations in its environment. Here, we investigated the role of 2-component regulatory systems (2CSs) in plague because the latter are known to be key players in bacterial adaptation to environmental change.

New insights into how Yersinia pestis adapts to its mammalian host during bubonic plague.

Bubonic plague (a fatal, flea-transmitted disease) remains an international public health concern. Although our understanding of the pathogenesis of bubonic plague has improved significantly over the last few decades, researchers have still not been able to define the complete set of Y. pestis genes needed for disease or to characterize the mechanisms that enable infection.

Inheritance of the lysozyme inhibitor Ivy was an important evolutionary step by Yersinia pestis to avoid the host innate immune response.

Background: Yersinia pestis (the plague bacillus) and its ancestor, Yersinia pseudotuberculosis (which causes self-limited bowel disease), encode putative homologues of the periplasmic lysozyme inhibitor Ivy and the membrane-bound lysozyme inhibitor MliC. The involvement of both inhibitors in virulence remains subject to debate.

Methods: Mutants lacking ivy and/or mliC were generated.

Efficacy of ciprofloxacin-gentamicin combination therapy in murine bubonic plague.

Potential benefits of combination antibiotic therapy for the treatment of plague have never been evaluated. We compared the efficacy of a ciprofloxacin (CIN) and gentamicin (GEN) combination therapy with that of each antibiotic administered alone (i) against Yersinia pestis in vitro and (ii) in a mouse model of bubonic plague in which animals were intravenously injected with antibiotics for five days, starting at two different times after infection (44 h and 56 h). In vitro, the CIN+GEN combination was synergistic at 0.

First case of postaneurysmal prosthetic vascular infection due to a nonsuperantigenic Yersinia pseudotuberculosis strain.

Among Yersinia spp., Y. enterocolitica is the species most frequently isolated from infected aneurysms.

A model of bacterial intestinal infections in Drosophila melanogaster.

Serratia marcescens is an entomopathogenic bacterium that opportunistically infects a wide range of hosts, including humans. In a model of septic injury, if directly introduced into the body cavity of Drosophila, this pathogen is insensitive to the host's systemic immune response and kills flies in a day. We find that S.

Detection and avoidance of a natural product from the pathogenic bacterium Serratia marcescens by Caenorhabditis elegans.

The nematode Caenorhabditis elegans is present in soils and composts, where it can encounter a variety of microorganisms. Some bacteria in these rich environments are innocuous food sources for C. elegans, whereas others are pathogens.

A generalized transducing phage (phiIF3) for the genomically sequenced Serratia marcescens strain Db11: a tool for functional genomics of an opportunistic human pathogen.

A bacteriophage (phiIF3) capable of mediating generalized transduction in Serratia marcescens strain Db11 has been isolated and characterized. The genome of this Serratia strain has recently been sequenced and is likely to become the reference strain for S. marcescens researchers.

Production of the cryptic EefABC efflux pump in Enterobacter aerogenes chloramphenicol-resistant mutants.

Objectives: AcrAB-TolC is the major tripartite multidrug efflux pump in Enterobacter aerogenes while EefABC is a cryptic efflux system. This study was conducted to identify and characterize E. aerogenes mutants producing the EefABC efflux pump.

The eefABC multidrug efflux pump operon is repressed by H-NS in Enterobacter aerogenes.

The Enterobacter aerogenes eefABC locus, which encodes a tripartite efflux pump, was cloned by complementation of an Escherichia coli tolC mutant. E. aerogenes deltaacrA expressing EefABC became less susceptible to a wide range of antibiotics.

Genetic models in pathogenesis.

To decipher the complexity of host-pathogen interactions the widest possible range of model hosts and of analytical methods is required. As some virulence mechanisms and certain host responses have been conserved throughout evolution, even simple organisms can be used as model hosts to help our understanding of infectious diseases. The availability of molecular genetic tools and a cooperative community of researchers are pivotal to the emergence of model systems.

Overexpression and purification of the three components of the Enterobacter aerogenes AcrA-AcrB-TolC multidrug efflux pump.

The tripartite AcrA-AcrB-TolC system is the major efflux pump of the nosocomial pathogen Enterobacter aerogenes. AcrA is a trimeric periplasmic lipoprotein anchored in the inner membrane, AcrB is an inner membrane transporter and TolC is a trimeric outer membrane channel. In order to reconstitute the AcrA-AcrB-TolC system of E.

The AcrAB-TolC efflux pump contributes to multidrug resistance in the nosocomial pathogen Enterobacter aerogenes.

We identified the genes encoding the AcrA-AcrB-TolC efflux pump in Enterobacter aerogenes and constructed acrAB and tolC mutants from a multidrug-resistant isolate. Both derivatives were more susceptible to antibiotics than the parental strain. Sequence analysis and complementation experiments revealed that the multidrug-resistant isolate is an acrR mutant.