Location: Meat Safety & Quality Research
Title: Gene expression response of multidrug resistant Salmonella enterica serovar Newport to simulated multiple hurdle beef carcass processing interventions Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 28, 2011
Publication Date: May 1, 2011
Citation: Harhay, D.M., Smith, T.P., Harhay, G.P. 2011. Gene expression response of multidrug resistant Salmonella enterica serovar Newport to simulated multiple hurdle beef carcass processing interventions. In: Proceedings of the American Society for Microbiology. 111th General Meeting of the American Society for Microbiology, May 21-24, 2011, New Orleans, Louisiana. 2011 CDROM. Meeting Abstract K-2692. Technical Abstract: Background: The foodborne pathogen Salmonella is a common contaminant of cattle hides at harvest. Hide contamination transferred to carcasses in the dressing process may enter the food chain and cause salmonellosis via the consumption of undercooked ground beef. In response, many processors have implemented interventions aimed at eliminating pathogens on carcasses. Despite their efforts, low-level pathogen prevalence on carcasses persists. Intervention survivors likely emerge in a resistant state, having adapted to the stressors imposed. However, little is known about the gene expression response of Salmonella serotypes commonly associated with cattle when exposed to carcass interventions. To address this knowledge gap, we characterized the transcriptome of a multidrug resistant (MDR) Salmonella Newport strain, in response to simulated beef carcass processing interventions. Methods: MDR S. Newport was challenged by sequential exposure to thermal stress (80°C), 2% lactic acid (55°C) and cold stress (4°C). Total RNA was isolated from challenged and control cultures. Purified mRNA was converted to cDNA and sequenced using the Roche 454 platform. Gene expression, measured by estimates of transcript abundance, was assessed by mapping cDNA sequences back to the annotated reference genome sequence. Results: In all, 94.5 Mb (challenged) and 84.7 Mb (control) of cDNA transcripts were sequenced. Intervention exposure resulted in the increased expression of 761 genes (approximately 16% of 4,613 genes examined). Genes demonstrating the greatest fold change included those with roles in the heat shock response, DNA repair, two component response regulators and a number of regulatory systems that govern the Salmonella virulence response. Conclusions: The expression profiles described present a picture of the molecular strategies Salmonella employs to survive multiple hurdle beef carcass processing interventions. These data may be used to combat the entry of Salmonella into the beef food chain.