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Fine-tuning carbapenem resistance by reducing porin permeability of bacteria activated in the selection process of conjugation.

ABSTRACT: Antibiotic resistance is an emerging public health issue. Plasmids are one of the popular carriers to disseminate resistance genes among pathogens. However, the response of plasmid-carrying bacteria to antibiotic treatment and how these bacteria evolve to increase their resistance remain elusive. In this study, we conjugated plasmid pNDM-HK to E. coli J53 recipient cells and selected survivors using different concentrations of the broad spectrum antibiotic meropenem. After selection, transconjugants conferred varying minimum inhibitory concentrations with respect to carbapenems. We sequenced and compared the transcriptomes of transconjugants that exhibited distinct carbapenem susceptibilities, and found that the loss of outer membrane proteins led to antibiotic resistance. Moreover, we identified a novel mutation, G63S, in transcription factor OmpR which moderates the expression of outer membrane proteins. The loss of porins was due to incapability of phosphorylation, which is essential for porin transcription and carbapenem resistance. We also characterized other genes that are regulated by ompR in this mutant, which contributed to bacterial antibiotic resistance. Overall, our studies suggest antibiotic pressure after conjugation might be an alternative pathway to promote antimicrobial resistance.

SUBMITTER: Kong HK

PROVIDER: S-EPMC6189183 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Fine-tuning carbapenem resistance by reducing porin permeability of bacteria activated in the selection process of conjugation.

Kong Hoi-Kuan HK Pan Qing Q Lo Wai-U WU Liu Xuan X Law Carmen O K COK Chan Ting-Fung TF Ho Pak-Leung PL Lau Terrence Chi-Kong TC

Scientific reports 20181015 1

Antibiotic resistance is an emerging public health issue. Plasmids are one of the popular carriers to disseminate resistance genes among pathogens. However, the response of plasmid-carrying bacteria to antibiotic treatment and how these bacteria evolve to increase their resistance remain elusive. In this study, we conjugated plasmid pNDM-HK to E. coli J53 recipient cells and selected survivors using different concentrations of the broad spectrum antibiotic meropenem. After selection, transconjug ...[more]

PMID: 30323356

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Project description:Rationale. The microvasculature of the central nervous system includes the blood-brain barrier (BBB), which regulates the permeability to nutrients and restricts the passage of toxic agents and inflammatory cells. Canonical Wnt/b-catenin signaling is responsible for the early phases of brain vascularization and blood-brain barrier differentiation. However, this signal declines after birth and other signaling pathways able to maintain barrier integrity at postnatal stage are still unknown. Objective. Sox17 constitutes a major downstream target of Wnt/b-catenin in endothelial cells and regulates arterial differentiation. In the present paper, we asked whether Sox17 may act downstream of Wnt/b-catenin in inducing BBB differentiation and maintenance. Methods and Results. Using reporter mice and nuclear staining of Sox17 and b-catenin, we report that while b-catenin signaling declines after birth, Sox17 activation increases and remains high in the adult. Endothelial-specific inactivation of Sox17 leads to increase of permeability of the brain microcirculation. The severity of this effect depends on the degree of BBB maturation: it is strong in the embryo, and progressively declines after birth. In search of Sox17 mechanism of action, RNA-Seq analysis of gene expression of brain endothelial cells has identified members of the Wnt/b-catenin signaling pathway as downstream targets of Sox17. Consistently, we found that Sox17 is a positive inducer of Wnt/b-catenin signaling and it acts in concert with this pathway to induce and maintain BBB properties. In vivo, inhibition of the b-catenin destruction complex or expression of a degradation-resistant b-catenin mutant, prevent the increase in permeability and retina vascular malformations observed in the absence of Sox17. Conclusions. Our data highlight a novel role for Sox17 in the induction and maintenance of the BBB and they underline the strict reciprocal tuning of this transcription factor and Wnt/b-catenin pathway. Modulation of Sox17 activity may be relevant to control BBB permeability in pathological conditions.

Project description:RationaleThe microvasculature of the central nervous system includes the blood-brain barrier (BBB), which regulates the permeability to nutrients and restricts the passage of toxic agents and inflammatory cells. Canonical Wnt/β-catenin signaling is responsible for the early phases of brain vascularization and BBB differentiation. However, this signal declines after birth, and other signaling pathways able to maintain barrier integrity at postnatal stage are still unknown.ObjectiveSox17 (SRY [sex-determining region Y]-box 17) constitutes a major downstream target of Wnt/β-catenin in endothelial cells and regulates arterial differentiation. In the present article, we asked whether Sox17 may act downstream of Wnt/β-catenin in inducing BBB differentiation and maintenance.Methods and resultsUsing reporter mice and nuclear staining of Sox17 and β-catenin, we report that although β-catenin signaling declines after birth, Sox17 activation increases and remains high in the adult. Endothelial-specific inactivation of Sox17 leads to increase of permeability of the brain microcirculation. The severity of this effect depends on the degree of BBB maturation: it is strong in the embryo and progressively declines after birth. In search of Sox17 mechanism of action, RNA sequencing analysis of gene expression of brain endothelial cells has identified members of the Wnt/β-catenin signaling pathway as downstream targets of Sox17. Consistently, we found that Sox17 is a positive inducer of Wnt/β-catenin signaling, and it acts in concert with this pathway to induce and maintain BBB properties. In vivo, inhibition of the β-catenin destruction complex or expression of a degradation-resistant β-catenin mutant, prevent the increase in permeability and retina vascular malformations observed in the absence of Sox17.ConclusionsOur data highlight a novel role for Sox17 in the induction and maintenance of the BBB, and they underline the strict reciprocal tuning of this transcription factor and Wnt/β-catenin pathway. Modulation of Sox17 activity may be relevant to control BBB permeability in pathological conditions.

Project description:BackgroundBurkholderia pseudomallei (Bps) is a Gram-negative bacterium that causes frequently lethal melioidosis, with a particularly high prevalence in the north and northeast of Thailand. Bps is highly resistant to many antimicrobial agents and this resistance may result from the low drug permeability of outer membrane proteins, known as porins.Principal findingsMicrobiological assays showed that the clinical Bps strain was resistant to most antimicrobial agents and sensitive only to ceftazidime and meropenem. An E. coli strain defective in most porins, but expressing BpsOmp38, exhibited considerably lower antimicrobial susceptibility than the control strain. In addition, mutation of Tyr119, the most prominent pore-lining residue in BpsOmp38, markedly altered membrane permeability, substitution with Ala (mutant BpsOmp38Y119A) enhanced uptake of the antimicrobial agents, while substitution with Phe (mutant BpsOmp38Y119F) inhibited uptake. Channel recordings of BpsOmp38 reconstituted in a planar black lipid membrane (BLM) suggested that the higher permeability of BpsOmp38Y119A was caused by widening of the pore interior through removal of the bulky side chain. In contrast, the lower permeability of BpsOmp38Y119F was caused by introduction of the hydrophobic side chain (Phe), increasing the 'greasiness' of the pore lumen. Significantly, liposome swelling assays showed no permeation through the BpsOmp38 channel by antimicrobial agents to which Bps is resistant (cefoxitin, cefepime, and doripenem). In contrast, high permeability to ceftazidime and meropenem was observed, these being agents to which Bps is sensitive.Conclusion/significanceOur results, from both in vivo and in vitro studies, demonstrate that membrane permeability associated with BpsOmp38 expression correlates well with the antimicrobial susceptibility of the virulent bacterium B. pseudomallei, especially to carbapenems and cephalosporins. In addition, substitution of the residue Tyr119 affects the permeability of the BpsOmp38 channel to neutral sugars and antimicrobial agents.

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Fine-tuning carbapenem resistance by reducing porin permeability of bacteria activated in the selection process of conjugation.

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Fine-tuning carbapenem resistance by reducing porin permeability of bacteria activated in the selection process of conjugation.

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