L. Monocytogenes in Food Processing Plants: Development and Implementation of Science-Based Environmental Testing and Control Stategies

Listeria monocytogenes is a foodborne pathogen that causes an estimated 2,500 annual disease cases and 500 deaths in the US. This organism is commonly found in many environments and most contamination of cooked ready-to-eat (RTE) foods appears to originate from the food processing plant environment. While a recent USDA directive encourages RTE meat plants to implement environmental testing programs, the relationships between the presence of L. monocytogenes in different environmental sites (e.g., drains, floors etc.) and finished product contamination has not been clearly established using quantitative criteria. The goal of this project is to integrate research, education, and extension efforts to develop science-based environmental testing and control strategies for L. monocytogenes and to deliver, implement, and evaluate these strategies in selected seafood, dairy, and meat processing plants. Our specific hypothesis is that there is a quantifiable relationship between the presence of L. monocytogenes in different processing environments and sites and contamination of product contact surfaces and finished products, which can be defined using mathematical modeling. The resulting models can be used to develop rational environmental control approaches that will lead to significant reductions of finished product contamination. We will use six RTE food plants as model systems to implement Listeria and L. monocytogenes testing procedures (including molecular subtyping) in order to characterize and quantify environmental contamination patterns and their relation to food contact surface and finished product contamination through development of mathematical transmission models. The mathematical models will be used to develop, implement, and evaluate improved environmental testing in three of the model plants. The economics of these improved strategies will also be evaluated. Workshops and training programs will be conducted to communicate and allow broad implementation of the testing programs developed. Specifically, we will accomplish the following objectives: 1. Use standard detection and molecular subtyping methods to characterize sources and spread of L. monocytogenes in 2 RTE seafood, 2 RTE meat, and 2 RTE dairy plants. 2. Based on the data obtained in objective 1, develop plant specific mathematical models under the framework of a modular process risk model (MPRM) to quantify and describe the relationship between the presence of L. monocytogenes in different environments and product contact surface and finished product contamination. 3. Develop and implement improved environmental Listeria control and testing strategies in 3 project plants and monitor their effects on food contact surface and finished product contamination. Complete an economic evaluation of the improved testing procedure. 4. Develop outreach and training programs to communicate and broadly implement recommended Listeria testing and control strategies. L. monocytogenes causes an estimated 500 foodborne deaths in the US annually. This organism is commonly found in many environments and most contamination of cooked ready-to-eat foods appears to originate from the food processing plant environment. This project will develop mathematical models of in-plant L. monocytogenes contamination pathways to allow rational design of intervention strategies. <p>
We have assembled a uniquely qualified consortium under the leadership of research, teaching and extension faculty at Cornell University and New York Sea Grant to integrate research, teaching and extension in the performance of this project. The project team includes individuals from several states and national organizations who have extensive experience in food safety. We will specifically apply the following approaches: 1. Select 2 RTE seafood, 2 RTE meat, and 2 RTE dairy plants in New York, Pennsylvania, Vermont and other states to collect raw material, environmental and finished product samples. Perform intensive daily sampling for 2 months in project year 1. Apply standard detection and molecular subtyping methods to test raw material, environmental, and finished product samples for L. monocytogenes and Listeria spp. Use prevalence and molecular subtyping data to analyze contamination patterns. 2. Use a modular process risk model (MPRM) framework to develop six comprehensive plant specific mathematical transmission models based on the data obtained from Obj.1. Compare the resulting models to the in-plant model developed by FSIS. Analyze the six models to determine whether a generic mathematical model can be developed. 3. Based on the Listeria contamination profiles and mathematical models generated, develop an improved environmental Listeria testing program to be implemented in 3 of the 6 study plants. Continue testing of environmental, raw material and finished product samples to evaluate the effectiveness of our Listeria sampling and testing program. Develop both a general 'Environmental Listeria Control Manual' and plant-specific Listeria testing plans, which will not only include testing sites and frequencies, but will also specify the corrections which should be implemented in response to Listeria positive test results. Calculate the overall costs of (i) the devised and optimized Listeria testing program implemented and (ii) the testing program in place before initiation of this project. Provide estimates on the benefits of the implemented testing programs, factoring in the likelihood of the program preventing a recall due to finished product contamination and the cost savings associated with prevented recalls. Calculate the change in specific benefits and costs as well as the net change. 4. Develop an extension publication that describes how RTE food processors can implement an improved L. monocytogenes environmental sampling and testing program in an individual plant. Develop a factsheet (approximately 4-5 pages in length) that will include step-by step guidelines for the implementation of the L. monocytogenes environmental sampling and testing program. Approximately 1000 copies of this factsheet will be produced and distributed to appropriate food safety information outlets. This factsheet will also be made available on the project WWW page. Conduct a series of three one-day 'Train-the-trainer' and industry workshops across the U.S. targeting various sectors of the RTE food industry to communicate our findings and to facilitate implementation of improved Listeria control strategies. <p>
The plant and commodity specific L. monocytogenes transmission models to be developed and refined through this project will provide industry and regulatory agencies with a more rational approach to identify and prioritize L. monocytogenes interventions in food processing plants.