Developing strategies to mitigate and control environmental Listeria monocytogenes in retail delis

Susan R Hammons, Purdue University

Abstract

There are many research avenues being investigated at institutions nationwide with the intent to reduce the public health risk of listeriosis. Approaches include studies on L. monocytogenes transmission dynamics in retail delis, observations of deli worker practices, a structured expert elicitation on transmission dynamics and statistical modeling of listeriosis risk impact factors. This thesis describes my contribution to the work being done in our group to (i) understand prevalence and persistence of L. monocytogenes and Listeria species non- monocytogenes on environmental surfaces (food contact and non-food contact); (ii) identify characteristics or practices which place stores at increased risk for L. monocytogenes contamination; and (iii) develop effective environmental control strategies which are feasible in the service-focused retail establishments. Chapter 1, "Listeria monocytogenes, Listeriosis, and Control Strategies: What the Retail Deli and Food Safety Manager Need to Know", is a review of published literature written at the invitation of Jeff Farber, Health Canada. It will be included in the book "Retail Food Safety" edited by Farber, Crichton, and Snyder and has been submitted to Springer for publication in spring 2014. This chapter is structured to (i) give retail food safety managers, store managers, and deli department managers an introduction to L. monocytogenes and listeriosis, (ii) identify foods and environmental surfaces of concern for L. monocytogenes contamination, and (iii) describe action-based control strategies deli managers and store managers can use to improve food safety practices and subsequently public health. Chapter 2, "Adenosine Triphosphate Levels Correlate to Probability of Listeria monocytogenes Contamination in Retail Delis" describes a study conducted in 15 retail delis among three states with environmental samples collected during preoperational and operational hours over nine months. Specifically this chapter discusses the relationships among concurrent samples for Adenosine Triphosphate (ATP), standard aerobic plate counts (APC), and the quantity of L. monocytogenes detected. It should be mentioned that the prevalence and persistence of L. monocytogenes and Listeria spp is not discussed in detail here as these data have been described by my collaborator Courtenay Simmons. The detected correlations between ATP response and the probability of detecting L. monocytogenes allowed us to develop recommended pass/fail limits to guide sanitation. With these limits, ATP testing is a potential rapid test for deli establishments to monitor the efficacy of daily sanitation procedures without significant investments in third-party auditing services or contract microbiological services. Chapter 3, "Evaluation of Deep Clean SSOP as a Listeria monocytogenes Control Strategy in Retail Delis" describes the development and testing of an intensive sanitation standard operating procedure, defined here as "deep cleaning." The SSOP was developed in collaboration with corporate food safety experts, retail sanitation providers, and from literature-based control strategies. The developed SSOP was evaluated in 9 retail deli establishments among three states. Labor was contracted out to a specially trained third party cleaning service crew (n=10) during a 12 h overnight shutdown period. The deep clean SSOP had varying immediate efficacy in delis with high L. monocytogenes prevalence and persistence and did not increase L. monocytogenes prevalence in stores with historically low L. monocytogenes prevalence. However, a single deep clean may not be sufficient to mitigate L. monocytogenes in some retail delis with evidence of persistence. (Abstract shortened by UMI.)

Degree

M.S.

Advisors

Oliver, Purdue University.

Subject Area

Food Science

COinS