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Influence of local and global regulators on efflux-mediated resistance of Salmonella enteritidis: contributions to a pleiotropic phenotype

Abstract number: S390

O'Regan E., Quinn T., Fanning S.

Salmonella Enteritidis is the most common aetiological agent of foodborne salmonellosis worldwide. Fluoroquinolones are the most widely used family of antibiotics in the treatment of life threatening salmonellosis. Of significant public health concern is the emergence of Salmonella isolates with reduced fluoroquinolone susceptibility. Resistance to fluoroquinolones is largely attributible to mutations in the quinolone resistance-determining regions (QRDRs) in target genes and overproduction of efflux pumps. In this paper we present data describing the role of local (eg: acrR) and global regulators (including marA, soxS, rob and ram) on efflux-mediated resistance (to nalidixic acid and ciprofloxacin) in field isolates and in in-vitro selected ciprofloxacin resistant Salmonella Enteritidis isolates. Gene expression was assessed by 'real-time' PCR and invasiveness was determined by co-culture of bacterial and CaCo-2 cells. The fitness cost of antibiotic resistance was examined and a high-throughput phenotype microarray was used to assess any pleiotropic effects.

Insertional mutants were constructed by P22 phage transduction using a number of these global regulators. The geno- and phenotypes of these mutants were re-examined to determine what (if any) effects these insertions had.

Based on this analysis, our findings do not support the adoption of a unifying functional model to describe regulation. Rather, these data suggest that the evolutonalry history of a strain may be a consideration in determining the influence that these regulators have in controlling gene expression of the RND efflux pump in S. Enteritidis along with some pleiotropic phenotypes.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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