Role of the efflux system EmrAB in multidrug resistance in Salmonella enterica Typhimurium

Abstract

Salmonella is a major contributor of cases of food-borne outbreak. Despite the decrease in the incidence of salmonellosis in recent years, an increase in the number of strains resistant to antibiotics is observed. Simultaneous resistance to several families of antibiotics is particularly important among serotype Typhimurium phage type DT104. Multiple resistance is due to associated specific mechanisms and the multi-species active efflux mechanism. Efflux allows the bacterium to reduce its intracellular concentration of toxic compounds and thus to survive in a hostile environment. In enteric bacteria, among the different carriers identified, AcrB plays an important role in the multiple resistance running in system of tripartite efflux AcrAB-TolC. However, in S. Typhimurium, another carrier than Cbra appears to play an important role in association with TolC in resistance to bile salts. EmrB, a carrier of the MFS family could play this role, thus, mutants inactivated at the level of the emrB gene and transcriptional regulator gene, emrR were built. Tests of susceptibility to antibiotics and bile salts have not shown significant differences between the parental strain and mutants. The complementation with the emrB gene did not amplify the fragment whereas, for each of the clones tested.