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 Strategies for Optimizing Salmonella Control
 

Strategies for Optimizing Salmonella Control

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Presented at 2013 Arkansas Association for Food Protection annual conference. ...

Presented at 2013 Arkansas Association for Food Protection annual conference.

Steven C. Ricke
Director of the Center for Food Safety
Wray Endowed Chair in Food Safety
Dept. of Food Science
University of Arkansas

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     Strategies for Optimizing Salmonella ControlStrategies for Optimizing Salmonella Control Presentation Transcript

    • Strategies for Optimizing Salmonella Control Steven C. Ricke Director of the Center for Food Safety Wray Endowed Chair in Food Safety Dept. of Food Science
    • Salmonella -Why Do We Care? • Infection and disease in humans - Mortalities - Cost $billions each year • Survivability in the Environment – Recontaminate food animals – Unpredictable reservoirs - pets – Difficult timeframe for traceback • Virulence and antibiotic resistance – Pathogenic phenotype – Dissemination of antibiotic resistance
    • What makes Salmonella pathogenic? – Pathogenicity = Ability to cause disease in the host – Virulence = Potency of infection – Virulence genes = Anything in the bacterial genome associated with pathogenesis
    • Regulation of Virulence in Salmonella External signals: pH, O2, iron, osmolarity, cation, organic acids, in vivo signals Induction of virulence genes = pathogenesis Pathogenesis = stress adaptation, adhesion, invasion, macrophage survival
    • Complexity of Salmonella Pathogenic Response • Multiple factors in the gastrointestinal tract • Variability in human/animal host response to Salmonella • Multiple environmental matrices during food processing = potential cross protection • Need: more comprehensive genetics
    • Sequence of Pathogen Genomes • Good news: Completed for more and more Salmonella serotypes • Bad news: Potential information is overwhelming!! • How do we use this tool kit to meet the needs of the food industry? – Tracking: Comparing sequences among isolates – Functional genomics: Identifying essential genes with unique functions for pathogenesis – Quantifying gene expression to understand regulation of pathogenesis
    • Quantifying Gene Expression: Transcriptional profiling of pathogens Transcriptional Profiling Overview Hybridization of labeled probes on microarray slide Measurement of Fluorescence in 2 channels red/green Data analysis Identification of differentially expressed genes Control Test RNA extraction from samples RNA Fluorescently Labeled cDNA Probes cDNA Application of microarray analysis of foodborne Salmonella in poultry production: A review. S.C. Ricke , A. Khatiwara , and Y.M. Kwon. 2013 Poultry Science 92 :2243– 2250.
    • Genomic Screening for Cross-Protection Potential in Salmonella to Antimicrobials A, B, or C Genes A-Resist Genes B-Resist Genes C-Resist Genes A-Resist Genes B-Resist Genes C-Resist No Cross protection = Optimal Extensive Cross protection = Not good Application of microarray analysis of foodborne Salmonella in poultry production: A review. S.C. Ricke , A. Khatiwara , and Y.M. Kwon. 2013 Poultry Science 92 :2243–2250.
    • Cross Protection - Genomic Studies • Combinations of heat and organic acids -Decrease viability: synergism -pH: 4.0 vs. 7.0 -Acid type: Acetate vs. propionate -Membrane disruption: K ion leakage • Transcriptome responses: – pH 4.0 and 55 C – Acetate and propionate similar genetically – Repression of heat shock genes – Membrane damage is key
    • Applications - Genomic Studies • Sudden shifts in pH may increase S. Typhimurium virulence level in a food matrix -How long? -Acid type • Thermal interaction with virulence should be considered • Chemical composition of food before and after physical processing may be a factor in virulence response Growth and transcriptional response of Salmonella Typhimurium LT2 to glucose–lysine-based Maillard reaction products generated under low water activity conditions. V. I. Chalova, O. Hernández-Hernández, A. Muthaiyan, S.A. Sirsat, S. Natesan, M. L. Sanz, F. J. Moreno, C. A. O'Bryan, P. G. Crandall, S.C. Ricke. 2012. Food Res. International. 45: 1044-1053.
    • How Do We Use The Results? Examples for Application of Salmonella Genomics - Cost effective control measures = High throughput screening for designing optimal multiple hurdles - Risk assessment or How safe does it need to be? Better models for food processing impact on infection potential -Vaccine technologies: Designing optimal vaccine targets
    • Thank You