Enhancing Microbial Food Safety by Risk Analysis

<p>NON-TECHNICAL SUMMARY: The goal of this project is the establishment of a multi-disciplinary network of scientists that performs comprehensive and integrated risk-based research and outreach to improve the safety of food from farm to fork. Interested stakeholders, including food producers and/or processors, retailers and consumers, have identified the need for an approach that conducts applied research to determine the prevalence and ecology of foodborne pathogens (including antibiotic resistant bacteria) in fresh and processed foods coupling that to research aimed at establishing effective control methods to decrease pathogen contamination of foods. </p>
<p>APPROACH: Food commodities will be obtained from producers, processors or purchased from local retailers or distributors. Samples will be stored at appropriate temperatures prior to use. Time between obtaining the food and experimental use will be minimized. Strains that have been associated with outbreaks from the commodity of interest will be used whenever possible. If not possible, other significant pathogenic strains will be selected. As appropriate, antibiotic-resistant variants of these strains have been isolated and several have been modified to produce florescent compounds, allowing enhanced detection from food systems. Validated non-pathogenic surrogate species of various microorganisms are also available for those situations where the use of such organisms may be appropriate. Strains of different genera can be engineered to contain traits noted above as required. The modifications will allow, when necessary, easy identification of the inoculated strains in the presence of high levels of background microflora. Inoculation. Inocula may be prepared from plate or broth cultures, and may or may not be washed prior to use. Appropriate carrier media will be used for inoculations at volumes, levels and methods typical for the commodity being evaluated. Standard methods will also be used to create viral or parasitic inocula. Methods for inoculation of food commodities will vary, as required, to best mimic standard commodity specific criteria and the specific hypothesis-based research questions being addressed. Recovery of Pathogens from Inoculated Samples. Sample sizes, buffering solutions, and maceration methods will vary depending upon commodity and experiment-specific requirements. Enumeration of bacterial pathogens following serial dilutions by standard plating techniques onto selective and non-selective media, Most Probable Number techniques or by more sophisticated molecular techniques are commonly used by project PIs. When samples fall below the limit of detection standard enrichment protocols (FDA BAM or others) will be followed. The collection of quantitative data will be encouraged whenever possible and can be used to populate risk models. Recovery of Pathogens from Environmental and Uninoculated Food Sources. Sampling methods to recover pathogens from the environment and foods will vary depending upon the sampling scheme and source as appropriate for the experimental design of the experiment. All attempts will be made by project PIs to not only determine frequency of pathogen isolation, but also concentration of pathogens identified, as concentration is a critical variable required in Objective 2. When appropriate, concentration techniques may be used to evaluate larger than typical sample volumes/weights and enrichment techniques used to evaluate samples when low numbers of cells are present. To accomplish the tasks associated with this objective, models and a risk management framework based on commodity-specific flow diagrams and inputs from the first objective will be developed. A key component of this activity will be the use of risk modeling techniques to relate levels of microbial contamination in food to the likelihood of the occurrence of foodborne outbreaks. The information developed using this approach will then be utilized to mitigate risks at specific points along the farm to fork continuum. The data developed using the risk modeling approaches will also lead to the identification of critical data gaps, which will feed back into new projects under objective 1. At harvest, methods will center around the combination of effective interventions that act synergistically to reduce or eliminate pathogens from foods, with a major emphasis placed on reducing cross contamination events that occur and lead to major food contamination events. Models and risk management. Predictive microbiology and quantitative microbial risk assessment (QMRA) are rapidly developing scientific disciplines that use mathematical equations, numerical data, and expert opinion to estimate the presence, survival, growth, and death of microbes in foods. These models allow for the prediction of the safety of a product, based on the entire sequence of events up to consumption. Temperature is a major extrinsic factor that affects growth/death of microorganisms and temperature of food products changes drastically during processing, storage, and distribution. Mathematical models will be developed to describe the chilling and heating rates of various food commodities. These developed models will be validated using real-life scenarios, whenever possible. Models to predict growth rate and lag time of pathogens as a function of temperature will be developed using the square root model popularized by Ratkowsky et al. (1991). The models generated for one commodity can be used to guide a series of experiments to validate the model for different, closely related commodities. Following the development of temperature models, expert opinion, industry, experimentally derived and literature data for processing and handling conditions to the point of consumption can be integrated into risk assessment models to estimate changes in microbial population dynamics. Alternatively, established models such as The Pathogen Modeling Program or ComBase can be utilized. Briefly, literature-captured data are collected by searching medical and biological databases for documents related to the commodity. A "flow diagram" documenting the commodity (including its ingredients) from production through retail should be developed with expert opinion. Data from other objectives and the literature will be translated into appropriate discrete or probability distribution functions and assigned to processes in the flow diagram. The QMRA model can be created using Analytica (Lumina Decision Systems, Los Gatos, CA) or @risk software (Palisade Corp). Results for simulated input distributions as well as final results will be obtained by running from 1,000 to 1,000,000+ iterations of the simulation. Tornado analysis can be used to determine the relative significance of the input variables. Comparison studies will include realistic HPP experiments in tissue culture media and model food products. Experimental variables for these studies will include pressure magnitude, treatment time, and temperature of different. HPP-treated RTE products will be evaluated using consumer taste panels (at another institution with IRB approval at that institution), allowing for consumers to be educated on foodborne viruses and the potential HPP impact on food safety and preservation. Maintaining proper temperature during transportation is essential to ensuring the safety of foods. In order to develop effective interventions, it is first necessary to understand the effects that cold chain temperature abuse have on the ability of bacterial foodborne pathogens to grow during transportation. Data from these studies will be used in risk assessment models to predicting the growth of foodborne bacterial pathogens during various stages of transport. A major area of concern with respect to contamination of food is the domestic kitchen, where multiple opportunities arise for abuse of foods. To address this concern, an additional evaluation of the efficacy of novel methods and products for washing produce to decrease populations of foodborne pathogens may be undertaken. Depending on the commodity, any number of methods could be evaluated. The most promising methods will be promoted through programs and educational materials developed in objective 3. Instead of relying solely on passive diffusion of information through the publication of Fact Sheets and peer-reviewed journal articles, and presentations, herein we propose to use two-way exchanges of information between stakeholders and researchers to tailor risk management messages for each specific audience. Multiple criteria will be used to evaluate and assess message content and media. </p>