P-026. Comparison of Transcriptomic Profiles of Salmonella enterica Enteritidis and Typhimurium under Oxidative Stress

S. Wang1, A. M. Phillippy2, D. S. Stewart3, S. L. Salzberg2, M. Tortorello3, W. Zhang1,4;
1Illinois Inst. of Technology, Summit, IL, 2Ctr. for Bioinformatics and Computational Biol., Univ. of Maryland, College Park, MD, 3US FDA Natl. Ctr. for Food Safety and Technology, Summit, IL, 4Natl. Ctr. for Food Safety and Technology, Illinois Inst. of Technology, Summit, IL.

Enteritidis and Typhimurium are the predominant Salmonella enterica serotypes associated with foodborne gastroenteritis in the U. S. It has been shown that Salmonella cells can rapidly adapt to and survive treatments of decontamination (using oxidative reagents such as chlorine or hydrogen peroxide) on fresh produce or food contact surfaces. However, the underlying mechanism of bacterial stress adaptation and sanitizer resistance is poorly understood. To determine how S. Enteritidis and S. Typhimurium strains respond to oxidative stress at transcriptional levels, we compared two fully sequenced Enteritidis and Typhimurium genomes; designed long oligonucleotide (60-mer) tiling microarrays that target all consensus and strain-specific genes in these genomes; and analyzed the global gene expression profiles of S. Enteritidis and S. Typhimurium under the exposure to sublethal concentrations of chlorine (390 ppm) and hydrogen peroxide (1 mM) in Brain Heart Infusion broth. We found 89 and 203 genes were significantly up-regulated (>2 fold p<0.1) under the chlorine treatment in S. Typhimurium and S. Enteritidis, respectively. Genes commonly up-regulated by both oxidative treatments included those involved in energy production and conversion, amino acid transport and metabolism, transcription, secondary metabolites biosynthesis, cell envelope biogenesis, posttranslational modification, and cellular signaling. A total of 181 genes were found to be differentially expressed (>2 fold p<0.1) in S. Typhimurium and S. Enteritidis, which included genes that potentially mediate iron-sulfur cluster formation, and genes encoding heat shock protein chaperons and putative outer membrane proteins important for biofilm formation through surface hydrophobicity. Knowledge gained about the specific genetic factors that play roles in the adaptation and resistance of Salmonella to oxidative stress may lead to developing more effective intervention strategies to lower the risk of contamination by this pathogen in foods and food processing plants.