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Accepted version

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2015-12-17

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Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/98843

Differential impact of ramRA mutations on both ramA transcription and decreased antimicrobial susceptibility in Salmonella Typhimurium.

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http://dx.doi/org/10.1093/jac/dkv410

Abstract

OBJECTIVES: This study was focused on analysing the heterogeneity of mutations occurring in the regulators of efflux-mediated MDR in Salmonella Typhimurium. Moreover, the impact of such mutations on impairing the transcription of ramA, acrB, tolC and acrF was also assessed as was the impact on the resistance or decreased susceptibility phenotype. METHODS: Strains were selected in vitro under increasing ciprofloxacin concentrations. Etest and broth microdilution tests were used to determine the MICs of several unrelated compounds. Screening of mutations in the quinolone target genes and MDR regulators was performed. RT-PCR analysis was used to detect the levels of expression of acrB, tolC, ompF, acrF, emrB, acrR, ramA, soxS and marA. RESULTS: All mutant strains showed increased MICs of most of the antimicrobials tested, with the exception of kanamycin. Mutations in the quinolone target genes did not occur in all the mutants, which all harboured mutations in the ramRA regulatory region. All the mutants overexpressed ramA, tolC and acrB (only tested in 60-wt derivatives), whereas differential results were seen for the remaining genes. CONCLUSIONS: Mutations in the ramRA region related to resistance and/or decreased susceptibility to antimicrobials predominate in Salmonella. There is heterogeneity in the types of mutations, with deletions affecting RamR-binding sites having a greater impact on ramA expression and the MDR phenotype.

Subject

Salmonel·la, Resistència als medicaments, Quinolones, Bacteris

Subject (English)

Salmonella, Drug resistance, Quinolone antibacterial agents, Bacteria

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Articles publicats en revistes (Fonaments Clínics)
Articles publicats en revistes (ISGlobal)

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FÀBREGA SANTAMARIA, Anna, BALLESTÉ DELPIERRE, Clara Celia and VILA ESTAPÉ, Jordi. Differential impact of ramRA mutations on both ramA transcription and decreased antimicrobial susceptibility in Salmonella Typhimurium. Journal of Antimicrobial Chemotherapy. 2015. Vol. 71, num. 3, pags. 617-624. ISSN 0305-7453. [consulted: 16 of August of 2026]. Available at: https://hdl.handle.net/2445/98843

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