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mexS

transcriptional repressor of MexEF-OprN efflux pump

NCBI Pathogen Isolates

Bacterial genomes carrying this gene

NCBI Reference Gene Catalog

Known alleles and reference sequences

Protein entries specific to mexS

Browse AMR rules for mexS

Validation StatusSupported

Overview

Mechanism: upregulation of mexEF-oprN multidrug efflux operon
Validation Method: mutant generation and MIC testing
Drug Classes: Fluoroquinolone, Chloramphenicol, Ciprofloxacin, Levofloxacin, Erythromycin, Tetracycline, Tigecycline, Imipenem|Relebactam, Fluoroquinolones, Ciprofloxacin|Levofloxacin, Ciprofloxacin|Norfloxacin|Imipenem|Meropenem, Imipenem, Meropenem, Tobramycin|Aztreonam, Ceftazidime-avibactam|Ceftolozane/tazobactam, Piperacillin/tazobactam|Ceftazidime|Cefepime|Meropenem|Imipenem|Tobramycin|Ciprofloxacin
Organisms: Pseudomonas aeruginosa, Pseudomonas aeruginosa PA7, Pseudomonas aeruginosa DSM 1128, Pseudomonas aeruginosa PA14, Pseudomonas aeruginosa clinical isolates
Papers: 15
Databases: Reslit
Mutations: 22

Mutations

Protein Change	Nucleotide Change	Mechanism	Organism	Resistance To	Database	Validation Status
D249N	-	-	Pseudomonas aeruginosa	CiprofloxacinCiprofloxacin\|Norfloxacin\|Imipenem\|Meropenem	Reslit	Candidate
G78S	-	-	-	Ciprofloxacin	Reslit	Candidate
G123R	-	-	Pseudomonas aeruginosa	Imipenem\|Relebactam

Papers15

1

Mechanisms decreasing in vitro susceptibility to the LpxC inhibitor CHIR-090 in the gram-negative pathogen Pseudomonas aeruginosa.

PMID 22024823 · 2012

The study identifies several mechanisms by which Pseudomonas aeruginosa can reduce susceptibility to the LpxC inhibitor CHIR-090, including mutations in efflux pump regulators (mexR, nfxB, mexS), overexpression of LpxC, and mutations in the fatty acid biosynthesis gene fabG.

Gene Information

Gene Name: mexS
Allele: mexS
Encodes: transcriptional repressor of MexEF-OprN efflux pump
Source Database: Reslit
Organisms Tested In: • Pseudomonas aeruginosa
Validation Method: mutant generation and MIC testing

2

Efflux-mediated fluoroquinolone resistance in the multidrug-resistant Pseudomonas aeruginosa clinical isolate PA7: identification of a novel MexS variant involved in upregulation of the mexEF-oprN multidrug efflux operon.

PMID 25653649 · 2015

The study identified a novel MexS variant (A155V) in Pseudomonas aeruginosa PA7 that leads to upregulation of the mexEF-oprN multidrug efflux operon, contributing to fluoroquinolone resistance. The mutation in mexS was shown to enhance resistance by increasing the expression of the efflux pump.

Gene Information

Gene Name: mexS
Allele: mexS
Encodes: transcriptional activator
Source Database: Reslit
Mechanism: upregulation of mexEF-oprN multidrug efflux operon
Confers Resistance To: Fluoroquinolone
Organisms Tested In: • Pseudomonas aeruginosa PA7
• Pseudomonas aeruginosa DSM 1128
Validation Method: mutant construction and MIC testing
Sequence Accession: AB889539

3

Amino Acid Substitutions Account for Most MexS Alterations in Clinical nfxC Mutants of Pseudomonas aeruginosa.

PMID 26833155 · 2016

Gene Information

Gene Name: mexS
Allele: mexS
Encodes: oxidoreductase
Source Database: Reslit
Mechanism: mutated mexS gene leads to activation of mexEF-oprN operon
Confers Resistance To: ChloramphenicolCiprofloxacin
Organisms Tested In: • Pseudomonas aeruginosa
Validation Method: cloning and complementation experiments

4

Mechanisms for Development of Ciprofloxacin Resistance in a Clinical Isolate of Pseudomonas aeruginosa.

PMID 33488544 · 2020

Gene Information

Gene Name: mexS
Allele: mexS
Encodes: putative oxidoreductase
Source Database: Reslit
Mechanism: mutation
Confers Resistance To: Ciprofloxacin
Organisms Tested In: • Pseudomonas aeruginosa
Validation Method: gene editing and MIC testing

5

Low Ciprofloxacin Concentrations Select Multidrug-Resistant Mutants Overproducing Efflux Pumps in Clinical Isolates of Pseudomonas aeruginosa.

PMID 36000896 · 2022

Low ciprofloxacin concentrations select for multidrug-resistant mutants in Pseudomonas aeruginosa clinical isolates, primarily through overproduction of efflux pumps mexCD-oprJ and mexEF-oprN, along with mutations in gyrA, parE, mexS, and nfxB.

Gene Information

Gene Name: mexS
Allele: mexS
Encodes: efflux pump regulator
Source Database: Reslit
Mechanism: overexpression of MexCD-OprJ and MexEF-OprN efflux pumps
Confers Resistance To: CiprofloxacinLevofloxacinChloramphenicolErythromycinTetracyclineTigecycline
Organisms Tested In: • Pseudomonas aeruginosa PA14
• Pseudomonas aeruginosa clinical isolates
Validation Method: sequencing of genes and expression analysis