Effects of Natural Mutations in the ramRA Locus on Invasiveness of Epidemic Fluoroquinolone-Resistant Salmonella enterica Serovar Typhimurium Isolates

Giraud, Étienne; Baucheron, Sylvie; Virlogeux-Payant, Isabelle; Nishino, Kunihiko; Cloeckaert, Axel

doi:10.1093/infdis/jis755

Cited by 16 publications

(20 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The mutations were distinct frame shift mutations and consisted of a GATC duplication for strain 02-2818, a G insertion for strain 05-8560, and a 91 bp deletion for strain 02-8141 (Figure 1). The role of these mutations in upregulating acrAB and tolC expression, and consecutive enhanced efflux-mediated resistance, was further assessed by: (i) complementing with the wild-type ramR gene (using plasmid pRamR Abouzeed et al, 2008); (ii) determining the MICs of ciprofloxacin and unrelated antibiotic florfenicol shown to be substrate of AcrAB-TolC (Baucheron et al, 2002); and (iii) measuring expression of ramA, acrA , and tolC by qRT-PCR (Giraud et al, 2013). The results shown in Table 3 are in agreement with data published previously for other S. enterica serovars (Abouzeed et al, 2008; Kehrenberg et al, 2009), i.e.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

ramR mutations affecting fluoroquinolone susceptibility in epidemic multidrug-resistant Salmonella enterica serovar Kentucky ST198

Baucheron¹,

Hello²,

Doublet³

et al. 2013

Front. Microbiol.

Self Cite

View full text Add to dashboard Cite

A screening for non-target mutations affecting fluoroquinolone susceptibility was conducted in epidemic multidrug-resistant Salmonella enterica serovar Kentucky ST198. Among a panel of representative isolates (n = 27), covering the epidemic, only three showed distinct mutations in ramR resulting in enhanced expression of genes encoding the AcrAB-TolC efflux system and low increase in ciprofloxacin MIC. No mutations were detected in other regulatory regions of this efflux system. Ciprofloxacin resistance in serovar Kentucky ST198 is thus currently mainly due to multiple target gene mutations.

show abstract

Section: Resultsmentioning

confidence: 99%

“…Occurrence of mutations affecting acrAB and tolC expression was determined by PCR and sequencing the regulatory regions ramR-ramA, acrR-acrA, marC -marO- marR-marA, soxS-soxR , and acrS-acrE using primers listed in Table 2. Transcription levels of ramA, acrA , and tolC were determined by qRT-PCR as described previously (Giraud et al, 2013). …”

Section: Methodsmentioning

confidence: 99%

ramR mutations affecting fluoroquinolone susceptibility in epidemic multidrug-resistant Salmonella enterica serovar Kentucky ST198

Baucheron¹,

Hello²,

Doublet³

et al. 2013

Front. Microbiol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…This work reports that changes in AraC-like global regulators (44), some of them associated with metabolic changes (45). In contrast to previous works that are focused on the effect of specific antimicrobials on laboratory strains (46-49), our work is based on the analysis of mutants derived from clinical isolates belonging to predominant E. coli and K. pneumoniae infective clones.…”

Section: Discussionmentioning

confidence: 99%

Polymorphic Variation in Susceptibility and Metabolism of Triclosan-Resistant Mutants of Escherichia coli and Klebsiella pneumoniae Clinical Strains Obtained after Exposure to Biocides and Antibiotics

Curião

Marchi

Viti

et al. 2015

Antimicrob Agents Chemother

View full text Add to dashboard Cite

Exposure to biocides may result in cross-resistance to other antimicrobials. Changes in biocide and antibiotic susceptibilities, metabolism, and fitness costs were studied here in biocide-selected Escherichia coli and Klebsiella pneumoniae mutants. E. coli and K. pneumoniae mutants with various degrees of triclosan susceptibility were obtained after exposure to triclosan (TRI), benzalkonium chloride (BKC), chlorhexidine (CHX) or sodium hypochlorite (SHC), and ampicillin or ciprofloxacin. Alterations in antimicrobial susceptibility and metabolism in mutants were tested using Phenotype MicroArrays. The expression of AcrAB pump and global regulators (SoxR, MarA, and RamA) was measured by quantitative reverse transcription-PCR (qRT-PCR), and the central part of the fabI gene was sequenced. The fitness costs of resistance were assessed by a comparison of relative growth rates. Triclosan-resistant (TRI r ) and triclosan-hypersusceptible (TRI hs ) mutants of E. coli and K. pneumoniae were obtained after selection with biocides and/or antibiotics. E. coli TRI r mutants, including those with mutations in the fabI gene or in the expression of acrB, acrF, and marA, exhibited changes in susceptibility to TRI, CHX, and antibiotics. TRI r mutants for which the TRI MIC was high presented improved metabolism of carboxylic acids, amino acids, and carbohydrates. In TRI r mutants, resistance to one antimicrobial provoked hypersusceptibility to another one(s). TRI r mutants had fitness costs, particularly marAoverexpressing (E. coli) or ramA-overexpressing (K. pneumoniae) mutants. TRI, BKC, and CIP exposure frequently yielded TRI r mutants exhibiting alterations in AraC-like global regulators (MarA, SoxR, and RamA), AcrAB-TolC, and/or FabI, and influencing antimicrobial susceptibility, fitness, and metabolism. These various phenotypes suggest a trade-off of different selective processes shaping the evolution toward antibiotic/biocide resistance and influencing other adaptive traits.

show abstract

“…RamA has also been reported to negatively influence virulence in Salmonella enterica serovar Typhimurium by downregulating SPI-1 expression 13 . However, this seems to be dependent on the genetic background of the strain 14 .…”

mentioning

confidence: 99%

The crystal structure of multidrug-resistance regulator RamR with multiple drugs

et al. 2013

Self Cite

View full text Add to dashboard Cite

RamR is a transcriptional repressor of the gene-encoding RamA protein, which controls the expression of the multidrug efflux system genes acrAB-tolC. RamR is an important multidrug-resistance factor, however, its structure and the identity of the molecules to which it responds have been unknown. Here, we report the crystal structure of RamR in complex with multiple drugs, including berberine, crystal violet, dequalinium, ethidium bromide and rhodamine 6G. All compounds are found to interact with Phe155 of RamR, and each compound is surrounded by different amino acid residues. Binding of these compounds to RamR reduces its DNA-binding affinity, which results in the increased expression of ramA. Our results reveal significant flexibility in the substrate-recognition region of RamR, which regulates the bacterial efflux participating in multidrug resistance.

show abstract

Effects of Natural Mutations in the ramRA Locus on Invasiveness of Epidemic Fluoroquinolone-Resistant Salmonella enterica Serovar Typhimurium Isolates

Abstract: ramRA mutations occurring in clinical FQ-resistant S. Typhimurium isolates may negatively modulate their invasiveness but this is strain-dependent.

Cited by 16 publications

References 35 publications

ramR mutations affecting fluoroquinolone susceptibility in epidemic multidrug-resistant Salmonella enterica serovar Kentucky ST198

ramR mutations affecting fluoroquinolone susceptibility in epidemic multidrug-resistant Salmonella enterica serovar Kentucky ST198

Polymorphic Variation in Susceptibility and Metabolism of Triclosan-Resistant Mutants of Escherichia coli and Klebsiella pneumoniae Clinical Strains Obtained after Exposure to Biocides and Antibiotics

The crystal structure of multidrug-resistance regulator RamR with multiple drugs

Contact Info

Product

Resources

About