Bile-mediated activation of the acrAB and tolC multidrug efflux genes occurs mainly through transcriptional derepression of ramA in Salmonella enterica serovar Typhimurium.

Objectives: In Salmonella Typhimurium, the genes encoding the AcrAB-TolC multidrug efflux system are mainly regulated by the ramRA locus, composed of the divergently transcribed ramA and ramR genes. The acrAB and tolC genes are transcriptionally activated by RamA, the gene for which is itself transcriptionally repressed by RamR. Previous studies have reported that bile induces acrAB in a ramA-dependent manner, but none provided evidence for an induction of ramA expression by bile.

Lack of efflux mediated quinolone resistance in Salmonella enterica serovars Typhi and Paratyphi A.

Salmonella enterica serovars Typhi and Paratyphi A isolates from human patients in France displaying different levels of resistance to quinolones or fluoroquinolones were studied for resistance mechanisms to these antimicrobial agents. All resistant isolates carried either single or multiple target gene mutations (i.e.