Development and Evaluation of Control Strategies for Listeria monocytogenes in Retail Deli Environments

Objectives

The goals of this project were to develop and implement new control strategies for L. monocytogenes in commercial retail delis and to test the ability of these strategies to reduce and control L. monocytogenes contamination.  The specific objectives were to:

Objective 1.         Develop practical and feasible control strategies to (i) reduce L. monocytogenes in retail deli environments and (ii) reduce L. monocytogenes cross-contamination of RTE deli meats handled at retail.

Objective 2.         Conduct a survey to identify additional potential risk-factors (e.g. deli design, sanitation practices, equipment manufacturer) which may contribute to L. monocytogenes persistence in retail deli environments. 

Objective 3.         Test the efficacy of control strategies developed in Obj.1 & 2 through implementation and follow-up testing in actual retail delis.

Conclusions

In this study,  L. monocytogenes was found to be prevalent in retail delis.  Non-food contact surfaces had higher L. monocytogenes prevalence than food contact surfaces.  Further, it was found that L. monocytogenes can persist over time but its continued persistence after implementation of enhanced control strategies may be due to failed execution of SSOPs.  Interventions strategies employed in this study significantly decreased L. monocytogenes prevalence in stores with moderate prevalence (5-10% samples positive).  Control strategies in the form of enhanced SSOPs were not sufficient to eliminate L. monocytogenes from highly prevalent and persistently contaminated stores indicating that more aggressive strategies (e.g., deep cleans, capital investment in redesign) may be necessary to fully mitigate persistent contamination.  Efficient, effective SSOP verifications strategies are greatly needed in the retail deli food system.  ATP testing may be a valuable tool to help ensure execution of SSOPs as well as useful as a training tool to demonstrate effective cleaning in retail delis.

Deliverables

A positive impact of this study is that targeted and enhanced SSOPs can reduce L. monocytogenes in retail delis with moderate prevalence.  Challenges remain around (i) efforts to reduce L. monocytogenes in delis with high prevalence and (ii) verification strategies to ensure execution of SSOPs in retail delis.