Fitness and molecular mechanisms of resistance to rifaximin in in vitro selected Escherichia coli mutants

Maria J. Pons, Laura Mensa, Joaquim Gascón, Joaquim Ruiz

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Abstract

Aims: This study sought to analyze the molecular mechanisms contributing to the development of rifaximin (Rfx) resistance in vitro in Escherichia coli. Twenty-eight Rfx-resistant mutants as well as four clinical isolates of E. coli were analyzed. The results obtained show that mutations in the rpoB gene and overexpression of Phe-Arg-β-naphthylamide (PAβN)-inhibitible efflux pump were implicated in Rfx resistance. Results: Amino acid substitutions at position 516 of the β-subunit of RNA polymerases were the most frequently obtained (53.6% of the mutants). The efflux pump inhibitor decreased the minimal inhibitory concentration (MIC) of 71.43% (20/28) of the mutant strains. Conclusions: Mutations studied in the rpoB gene and overexpression of PAβN-inhibitible efflux pumps contribute to Rfx resistance (together or not), whereas alterations in porin levels do not seem to have a relevant role in the acquisition of Rfx resistance.

Original languageEnglish
Pages (from-to)376-379
Number of pages4
JournalMicrobial Drug Resistance
Volume18
Issue number4
DOIs
StatePublished - 1 Aug 2012

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