Location: Egg Safety & Quality ResearchTitle: Differential Transcriptional Regulation Between Egg-contaminating and Non-egg-contaminating Strains of Salmonella Enteritidis Author
Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 1/17/2012
Publication Date: 6/16/2012
Citation: Orfe, L., Desai, P.T., Shah, D., Call, D.R., Guard, J.Y., Shah, D.H. 2012. Differential Transcriptional Regulation Between Egg-contaminating and Non-egg-contaminating Strains of Salmonella Enteritidis. American Society for Microbiology. p. B-2739. Interpretive Summary:
Technical Abstract: Background: Salmonella Enteritidis (SE) is the most common cause of food-borne salmonellosis primarily transmitted by contaminated poultry eggs. Despite its genetically clonal nature, SE strains differ markedly in their ability to disseminate systemically in chickens and subsequently invade the internal contents of an intact egg. A recent comparative whole genome mutational mapping revealed a total of 250 single nucleotide polymorphisms that differentiated the two genetically clonal PT13a strains which markedly vary in their ability to contaminate eggs and to form biofilm. The objective of this study was to determine the differences in the global transcriptional profiles between the egg-contaminating and non-egg contaminating SE strain. Methods: Three strains of SE (G1, G2 and G3) that vary genotypically and phenotypically were used for this study. Strains G2 and G3 were of the same phage type (PT13a), but distinctly different in their ability to form biofilms and contaminate eggs (G2=BF-EC+; G3=BF+EC-). Both PT13a strains were compared directly to strain G1 (PT4 22079), which contaminates eggs and forms biofilm (BF+, EC+). All strains were grown to stationary phase at 25°C, 37°C and 42°C, RNA was extracted, reverse-transcribed, labeled and hybridized to a SE whole genome microarray. Each strain-temperature combination was tested in triplicate and the data was analyzed using the R package LIMMA. Results: A total of 114 genes were differentially regulated by =2 fold (with 10% FDR) between all three strains at all temperatures tested. These included genes involved in various metabolic processes (26), cellular processes and signaling (26), cell envelope biogenesis (9), energy production (6), unknown functions (26) and others (20). Because the normal body temperature of chickens is 42°C, the differences between the G2 and G3 strains at 42°C may be relevant to egg contamination. A total of 26 genes were identified as being differentially expressed between G1 and G2 strains. Nine genes were upregulated in G2 included genes encoding zinc peptidase (yhjJ), curlin fimbriae (csgA), oxidative stress response (msrA) and unknown functions. Sixteen genes were down-regulated in G2 including majority of genes whose functions are unknown. Summary: These results show differential transcriptional regulation between egg-contaminating and non-egg contaminating strains.