[Characterization of gene expression associated with both the AcrAB/TolC system and the membrane permeability, in Salmonella spp isolates with and without gyrA mutation]

Introduction. The marA, soxS, ramA, acrB and ompF genes have been studied in order to characterize mechanisms of AcrAB-TolC active efflux pumps and membrane permeability alterations that reduce fluoroquinolones susceptibility in Salmonella spp. Methods. Mutations in marA, soxS, ramA, acrB and ompF genes were detected, as well as their expression levels in presence and absence of ciprofloxacin, calculating the level of change between them by qPCR. Data were analysed by using SPSS 19.0. Results. No mutations in these genes were found, but both AcrAB-TolC regulatory genes and structural acrB gene expression were affected by ciprofloxacin in both mutant strains and wild type bacterial strains (WT). The activation of the marA gene in presence of drug was higher in WT strains (level of change 0.823) than in mutants strains (level of change 0.158; p=0.049). In gyrA mutants, a reduction in ompF gene expression in presence of ciprofloxacin was found (level of change -0.949 p=0.017). Conclusion. The reduction of fluoroquinolones susceptibility in Salmonella spp is a complex process, in which several different bacterial mechanisms are involved. This study has found a high difference in the degree of participation among studied mechanisms, between bacterial strains with and without gyrA mutation. Whereas WT strains activated efflux pumps especially through marA gene, mutants supressed ompF gene expression related to porins.