Abstract
Salmonella enterica is an important enteric pathogen, and its various serovars cause both systemic and intestinal diseases in humans and domestic animals. The emergence of multidrug-resistant strains of Salmonella, leading to increased morbidity and mortality, has further complicated its management. Hfq is an RNA chaperon that mediates the binding of small RNAs to mRNA and assists in post-transcriptional gene regulation in bacteria. Although Hfq is related to important phenotypes including virulence in Salmonella, its role in the drug resistance of this organism is unknown. The aim of this study was to investigate the role of Hfq in intrinsic drug resistance of S. enterica serovar Typhimurium. hfq Mutant was susceptible to acriflavine. Although there is a relationship between the production of the AcrB multidrug efflux pump and Hfq in Escherichia coli, the deletion of the drug efflux acrB did not impair the effect of hfq deletion on Salmonella susceptibility. In contrast, the deletion of another drug efflux gene, smvA, impaired the effect of hfq deletion on acriflavine susceptibility. These results indicate that Hfq regulates the intrinsic drug resistance, and it may influence drug susceptibility by regulating SmvA in Salmonella.
Highlights
Salmonella causes a variety of diseases in humans, ranging from gastroenteritis to bacteremia and typhoid fever (Scherer and Miller, 2001)
We reveal that SmvA and not the AcrB drug efflux system contributes to the Hfq-mediated drug resistance of Salmonella, whereas it has been reported that AcrB contributes to the Hfq-mediated drug resistance of Escherichia coli
Hfq AFFECTS THE INTRINSIC DRUG SUSCEPTIBILITY OF SALMONELLA To investigate the role of Hfq in drug susceptibilities, hfq was deleted from S. enterica serovar Typhimurium strain ATCC 14028s, as described in the Section “Materials and Methods.”
Summary
Salmonella causes a variety of diseases in humans, ranging from gastroenteritis to bacteremia and typhoid fever (Scherer and Miller, 2001). We previously demonstrated that S. enterica serovar Typhimurium has nine functional drug efflux pumps (Nishino et al, 2006). In addition to these pumps, it has been reported that SmvA is an important efflux pump for acriflavine and related compounds (Villagra et al, 2008). Because many of these multidrug efflux pumps have overlapping substrate spectra, it is intriguing that bacteria, with their economically organized genomes, harbor such large sets of multidrug efflux genes. Available data indicate that multidrug efflux pumps are often expressed under precise and elaborate transcriptional control (Ahmed et al, 1994; Lomovskaya et al, 1995; Brooun et al, 1999; Grkovic et al, 2002)
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