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Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling

The hyperproduction of the chromosomal AmpC β-lactamase is the main mechanism driving β-lactam resistance in Pseudomonas aeruginosa, one of the leading opportunistic pathogens causing nosocomial acute and chronic infections in patients with underlying respiratory diseases. In the current scenario of...

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Autores principales: Torrens, Gabriel, Hernández, Sara Belén, Ayala, Juan Alfonso, Moya, Bartolome, Juan, Carlos, Cava, Felipe, Oliver, Antonio
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Society for Microbiology 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6890930/
https://www.ncbi.nlm.nih.gov/pubmed/31796566
http://dx.doi.org/10.1128/mSystems.00524-19
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author Torrens, Gabriel
Hernández, Sara Belén
Ayala, Juan Alfonso
Moya, Bartolome
Juan, Carlos
Cava, Felipe
Oliver, Antonio
author_facet Torrens, Gabriel
Hernández, Sara Belén
Ayala, Juan Alfonso
Moya, Bartolome
Juan, Carlos
Cava, Felipe
Oliver, Antonio
author_sort Torrens, Gabriel
collection PubMed
description The hyperproduction of the chromosomal AmpC β-lactamase is the main mechanism driving β-lactam resistance in Pseudomonas aeruginosa, one of the leading opportunistic pathogens causing nosocomial acute and chronic infections in patients with underlying respiratory diseases. In the current scenario of the shortage of effective antipseudomonal drugs, understanding the molecular mechanisms mediating AmpC hyperproduction in order to develop new therapeutics against this fearsome pathogen is of great importance. It has been accepted for decades that certain cell wall-derived soluble fragments (muropeptides) modulate AmpC production by complexing with the transcriptional regulator AmpR and acquiring different conformations that activate/repress ampC expression. However, these peptidoglycan-derived signals have never been characterized in the highly prevalent P. aeruginosa stable AmpC hyperproducer mutants. Here, we demonstrate that the previously described fragments enabling the transient ampC hyperexpression during cefoxitin induction (1,6-anhydro-N-acetylmuramyl-pentapeptides) also underlie the dacB (penicillin binding protein 4 [PBP4]) mutation-driven stable hyperproduction but differ from the 1,6-anhydro-N-acetylmuramyl-tripeptides notably overaccumulated in the ampD knockout mutant. In addition, a simultaneous greater accumulation of both activators appears linked to higher levels of AmpC hyperproduction, although our results suggest a much stronger AmpC-activating potency for the 1,6-anhydro-N-acetylmuramyl-pentapeptide. Collectively, our results propose a model of AmpC control where the activator fragments, with qualitative and quantitative particularities depending on the pathways and levels of β-lactamase production, dominate over the repressor (UDP-N-acetylmuramyl-pentapeptide). This study represents a major step in understanding the foundations of AmpC-dependent β-lactam resistance in P. aeruginosa, potentially useful to open new therapeutic conceptions intended to interfere with the abovementioned cell wall-derived signaling. IMPORTANCE The extensive use of β-lactam antibiotics and the bacterial adaptive capacity have led to the apparently unstoppable increase of antimicrobial resistance, one of the current major global health challenges. In the leading nosocomial pathogen Pseudomonas aeruginosa, the mutation-driven AmpC β-lactamase hyperproduction stands out as the main resistance mechanism, but the molecular cues enabling this system have remained elusive until now. Here, we provide for the first time direct and quantitative information about the soluble cell wall-derived fragments accounting for the different levels and pathways of AmpC hyperproduction. Based on these results, we propose a hierarchical model of signals which ultimately govern ampC hyperexpression and resistance.
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spelling pubmed-68909302019-12-16 Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling Torrens, Gabriel Hernández, Sara Belén Ayala, Juan Alfonso Moya, Bartolome Juan, Carlos Cava, Felipe Oliver, Antonio mSystems Research Article The hyperproduction of the chromosomal AmpC β-lactamase is the main mechanism driving β-lactam resistance in Pseudomonas aeruginosa, one of the leading opportunistic pathogens causing nosocomial acute and chronic infections in patients with underlying respiratory diseases. In the current scenario of the shortage of effective antipseudomonal drugs, understanding the molecular mechanisms mediating AmpC hyperproduction in order to develop new therapeutics against this fearsome pathogen is of great importance. It has been accepted for decades that certain cell wall-derived soluble fragments (muropeptides) modulate AmpC production by complexing with the transcriptional regulator AmpR and acquiring different conformations that activate/repress ampC expression. However, these peptidoglycan-derived signals have never been characterized in the highly prevalent P. aeruginosa stable AmpC hyperproducer mutants. Here, we demonstrate that the previously described fragments enabling the transient ampC hyperexpression during cefoxitin induction (1,6-anhydro-N-acetylmuramyl-pentapeptides) also underlie the dacB (penicillin binding protein 4 [PBP4]) mutation-driven stable hyperproduction but differ from the 1,6-anhydro-N-acetylmuramyl-tripeptides notably overaccumulated in the ampD knockout mutant. In addition, a simultaneous greater accumulation of both activators appears linked to higher levels of AmpC hyperproduction, although our results suggest a much stronger AmpC-activating potency for the 1,6-anhydro-N-acetylmuramyl-pentapeptide. Collectively, our results propose a model of AmpC control where the activator fragments, with qualitative and quantitative particularities depending on the pathways and levels of β-lactamase production, dominate over the repressor (UDP-N-acetylmuramyl-pentapeptide). This study represents a major step in understanding the foundations of AmpC-dependent β-lactam resistance in P. aeruginosa, potentially useful to open new therapeutic conceptions intended to interfere with the abovementioned cell wall-derived signaling. IMPORTANCE The extensive use of β-lactam antibiotics and the bacterial adaptive capacity have led to the apparently unstoppable increase of antimicrobial resistance, one of the current major global health challenges. In the leading nosocomial pathogen Pseudomonas aeruginosa, the mutation-driven AmpC β-lactamase hyperproduction stands out as the main resistance mechanism, but the molecular cues enabling this system have remained elusive until now. Here, we provide for the first time direct and quantitative information about the soluble cell wall-derived fragments accounting for the different levels and pathways of AmpC hyperproduction. Based on these results, we propose a hierarchical model of signals which ultimately govern ampC hyperexpression and resistance. American Society for Microbiology 2019-12-03 /pmc/articles/PMC6890930/ /pubmed/31796566 http://dx.doi.org/10.1128/mSystems.00524-19 Text en Copyright © 2019 Torrens et al. https://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Research Article
Torrens, Gabriel
Hernández, Sara Belén
Ayala, Juan Alfonso
Moya, Bartolome
Juan, Carlos
Cava, Felipe
Oliver, Antonio
Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling
title Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling
title_full Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling
title_fullStr Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling
title_full_unstemmed Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling
title_short Regulation of AmpC-Driven β-Lactam Resistance in Pseudomonas aeruginosa: Different Pathways, Different Signaling
title_sort regulation of ampc-driven β-lactam resistance in pseudomonas aeruginosa: different pathways, different signaling
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6890930/
https://www.ncbi.nlm.nih.gov/pubmed/31796566
http://dx.doi.org/10.1128/mSystems.00524-19
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