Food Protection Trends - November 2008 - 810

In summary, to ensure food safety and security of globally transported food there is a need for developing science based harmonized microbial testing criteria. While plausible from a scientific standpoint, politically this may be very difficult. Finally, performance based standards may be the fastest route to harmonization. S4 – Bacterial Physiology — A Forgotten theme that is Critical for the Food Microbiologist Diego Paiva, Auburn University and Bala Jagadeesan, Purdue University The symposium focused on the effect of stress and growth environment on bacterial physiology and its implication in food microbiology. The presenters were Charles Kaspar, Kathryn Boor, Roy Betts, Teresa Bergholz, Larry Beuchat and Martin Wiedmann. The complexity of the molecular interactions in regulating the phenotypic expression of the bacteria during growth and stress conditions at the transcriptional, translational and post translational level were discussed in depth along with the role of master regulators such as Histone Nucleoid Structure Proteins (H-NS). Stress response and virulence gene expression regulation by sigma B factor in Listeria monocytogenes was highlighted to emphasize the importance of understanding the role of general stress response factors in the survival and virulence of foodborne pathogens in general – L. monocytogenes in particular. The diverse growth and adaptive response of Salmonella to complex food matrix and growth parameter interactions helped reinforce the fact that each food system is unique and thus the physiological response of the bacteria could considerably vary depending on food. In addition, the species, strain, age of the cells and the culture growth phase play a very important role on metabolism and physiological response of bacterial cells to stressful environments. Another very important factor which affects bacterial survival and growth is the food in question and how this specific food is processed, prepared for consumption and commercialized. Some other factors within food composition such as water activity, pH, nutrient availability and physical state of food (liquid, paste, solid) must also be taken in consideration while preparing the inoculum for challenge studies. The difference between shock response and continuous response was explained in Escherichia coli O157:H7 and its impact in conferring cross protection, resistance to antimicrobials, design of challenge studies and food processing environment were discussed. Finally, the bacterial physiology and its effect on pathogen detection sensitivity using genetic, protein based and traditional approaches were discussed in detail. Specifically with the development of rapid detection methods, the need to understand about the physiological status of the bacteria enriched for a shorter duration was stressed upon. Thus the symposium emphasized the complexity of the molecular networks regulating the bacterial phenotypic expression under different growth and stress conditions. The symposium also focused on the applied aspects of the basic knowledge gained in areas such as design of challenge studies and effect on pathogen detection systems. S5 – Sampling and Sample Prep: Unglamorous but very necessary Heidi Weinkauf, Iowa State University and Michele Yabes-Manuzon, The Ohio State University Sampling and sample preparation are two key steps for the effective detection of microorganisms. However, most of the research to date has focused on developing assay technologies. Nonetheless, without reliable upstream methods, these detection procedures can be ineffective. Mary Lou Tortorello from FDA-CFSAN stressed the need to develop alternative methods without the use of culture enrichment. In order to advance research in this area, a sample prep multi-disciplinary working group was formed in July 2007 to help promote research in sampling and sample preparation methods for rapid food analyses. Byron Brehm-Stecher from Iowa State University discussed what comprises the most effective sample preparation methods. He pointed out that techniques and concepts could be borrowed from both allied and non-related fields to help improve sample prep methods. Improvements in these upstream methods are needed to address the physical challenges posed by the food matrix, and may eventually enable the direct analysis from the food without the isolation of cells. Emilio Esteban of USDA-FSIS-OPHS emphasized that the sampling method of choice depends on the questions that need to be answered. He discussed the basis of designing surveillance and monitoring systems. This requires defining the purpose and most appropriate sample prep procedures, applying the method, analyzing the results and then making recommendations and implementing the ideas. Tony Sharpe of Filtaflex Ltd. gave a historical overview of common approaches to sample preparation. The development of the stomacher in the 1970s was discussed along with alternatives that have since been created. The stomacher is a traditional method that is still widely used, however 810 FOOD PROTECTION TRENDS | NOVEMBER 2008

Food Protection Trends - November 2008

Table of Contents for the Digital Edition of Food Protection Trends - November 2008