Investigation of rpoS and dps Genes in Sodium Hypochlorite Resistance of Salmonella Enteritidis SE86 Isolated from Foodborne Illness Outbreaks in Southern Brazil.

In Rio Grande do Sul, southern Brazil, Salmonella Enteritidis is one of the principal microorganisms responsible for foodborne disease. The present study was conducted to compare the sodium hypochlorite resistance of Salmonella Enteritidis SE86 with that of other strains of Salmonella Enteritidis isolated from different regions of the world and to investigate the involvement of the rpoS and dps genes in resistance to this disinfectant. We tested five Salmonella Enteritidis wild-type (WT) strains isolated from different countries, two mutant strains of Salmonella Enteritidis SE86, and two tagged (3XFLAG) strains of Salmonella Enteritidis SE86 for their resistance to sodium hypochlorite (200 ppm). The survival of the WT and attenuated strains was determined based on bacterial counts, and tagged proteins (Dps and RpoS) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with anti-FLAG antibodies. None of the WT strains of Salmonella Enteritidis were totally inactivated after 20 min. The SE86 strain lacking dps was more sensitive to sodium hypochlorite than was the WT SE86 strain, with a 2-log reduction in counts after 1 min. The RpoS and Dps proteins were actively expressed under the conditions tested, indicating that in Salmonella Enteritidis SE86 these genes, which are expressed when in contact with sodium hypochlorite, are related to oxidative stress. [ABSTRACT FROM AUTHOR]