L. MONOCYTOGENES IN FOOD PROCESSING PLANTS: DEVELOPMENT AND IMPLEMENTATION OF SCIENCE-BASED ENVIRONMENTAL TESTING AND CONTROL STRATEGIES

Dr. Martin Wiedmann

Abstract

NON-TECHNICAL SUMMARY: 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.

OBJECTIVES: 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.