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Postprocessing contamination in processing plants has historically been a significant source of Listeria monocytogenes in ready-to-eat delicatessen meats, and therefore a major cause of human listeriosis cases and outbreaks. Recent risk assessments suggest that a majority of human listeriosis cases linked to consumption of contaminated deli meats may be due to L. monocytogenes contamination that occurs at the retail level. To better understand the ecology and transmission of Listeria spp. in retail delicatessens, food and nonfood contact surfaces were tested for L. monocytogenes and other Listeria spp. in a longitudinal study conducted in 30 retail delis in three U.S. states. In phase I of the study, seven sponge samples were collected monthly for 3 months in 15 delis (5 delis per state) prior to start of daily operation; in phase II, 28 food contact and nonfood contact sites were sampled in each of 30 delis during daily operation for 6 months. Among the 314 samples collected during phase I, 6.8% were positive for L. monocytogenes. Among 4,503 samples collected during phase II, 9.5% were positive for L. monocytogenes; 9 of 30 delis showed low L. monocytogenes prevalence (<1%) for all surfaces. A total of 245 Listeria spp. isolates, including 184 Listeria innocua, 48 Listeria seeligeri, and 13 Listeria welshimeri were characterized. Pulsed-field gel electrophoresis (PFGE) was used to characterize 446 L. monocytogenes isolates. PFGE showed that for 12 of 30 delis, one or more PFGE types were isolated on at least three separate occasions, providing evidence for persistence of a given L. monocytogenes subtype in the delis. For some delis, PFGE patterns for isolates from nonfood contact surfaces were distinct from patterns for occasional food contact surface isolates, suggesting limited cross-contamination between these sites in some delis. This study provides longitudinal data on L. monocytogenes contamination patterns in retail delis, which should facilitate further development of control strategies in retail delis.

According to the U.S. Food and Drug Administration's (FDA's) rule on \"Prevention of Salmonella Enteritidis in Shell Eggs during Production, Storage, and Transportation,\" shell eggs intended for human consumption are required to be held or transported at or below 45°F (7.2°C) ambient temperature beginning 36 h after time of lay. Meanwhile, eggs in hatcheries are typically stored at a temperature of 65°F (18.3°C). Although most of those eggs are directed to incubators for hatching, excess eggs have the potential to be diverted for human consumption as egg products through the \"breaker\" market if these eggs are refrigerated in accordance with FDA's requirement. Combining risk assessment models developed by the U.S. Department of Agriculture's Food Safety and Inspection Service for shell eggs and for egg products, we quantified and compared Salmonella Enteritidis levels in eggs held at 65°F versus 45°F, Salmonella Enteritidis levels in the resulting egg products, and the risk of human salmonellosis from consumption of those egg products. For eggs stored 5 days at 65°F (following 36 h at 75°F [23.9°C] in the layer house), the mean level of Salmonella Enteritidis contamination is 30-fold higher than for eggs stored at 45°F. These increased levels of contamination lead to a 47-fold increase in the risk of salmonellosis from consumption of egg products made from these eggs, with some variation in the public health risk on the basis of the egg product type (e.g., whole egg versus whole egg with added sugar). Assuming that 7% of the liquid egg product supply originates from eggs stored at 65°F versus 45°F, this study estimates an additional burden of 3,562 cases of salmonellosis per year in the United States. A nominal range uncertainty analysis suggests that the relative increase in the risk linked to the storage of eggs at higher temperature estimated in this study is robust to the uncertainty surrounding the model parameters. The diversion of eggs from broiler production to human consumption under the current storage practices of 65°F (versus 45°F) would present a substantive overall increase in the risk of salmonellosis.

Ready-to-eat (RTE) meat and poultry product samples collected between 2005 and 2017 from RTE-producing establishments for the U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) ALLRTE/RTEPROD_RAND (random) and RTE001/RTEPROD_RISK (risk-based) sampling projects were tested for Listeria monocytogenes (Lm). Data for 45,897 ALLRTE/RTEPROD_RAND samples collected from 3,607 distinct establishments and 112,347 RTE001/RTEPROD_RISK samples collected from 3,283 distinct establishments were analyzed for the presence of Lm. These data were also analyzed based upon the percentages of establishments with positive samples, annual production volume, sanitation control alternatives, geographic location, and season or month of sample collection. Results revealed low occurrence of Lm-positive samples from the random and risk-based sampling projects, with 152 (0.33%) positive samples for ALLRTE/RTEPROD_RAND and 403 (0.36%) positive samples for RTE001/RTEPROD_RISK. The percentage of positive samples significantly decreased over time, from about 0.7% in 2005 and 2006 to about 0.2% in 2017 (P < 0.05). From 2005 to 2017, 3.9% of establishments sampled under the ALLRTE/RTEPROD_RAND sampling project had at least one Lm-positive sample. Similarly, 10.0% of establishments sampled under the RTE001/RTEPROD_RISK sampling project had at least one positive sample. Samples positive for Lm were found in all geographic regions in all months. Thus, in 13 years of RTE product sampling in FSIS-regulated establishments (2005 through 2017), <0.4% of samples were positive for Lm in both risk-based and random sampling projects. The low prevalence of Lm in these products suggests that the combination of FSIS policies and industry practices may be effective for controlling Lm contamination. Information obtained from these sampling projects is relevant to the ongoing prevention of foodborne Lm illnesses from RTE meat and poultry products.

Cross-contamination, improper holding temperatures, and insufficient sanitary practices are known retail practices that may lead to product contamination and growth of Listeria monocytogenes. However, the relative importance of control options to mitigate the risk of invasive listeriosis from ready-to-eat (RTE) products sliced or prepared at retail is not well understood. This study illustrates the utility of a quantitative risk assessment model described in a first article of this series (Pouillot, R., D. Gallagher, J. Tang, K. Hoelzer, J. Kause, and S. B. Dennis, J. Food Prot. 78:134-145, 2015) to evaluate the public health impact associated with changes in retail deli practices and interventions. Twenty-two mitigation scenarios were modeled and evaluated under six different baseline conditions. These scenarios were related to sanitation, worker behavior, use of growth inhibitors, cross-contamination, storage temperature control, and reduction of the level of L. monocytogenes on incoming RTE food products. The mean risk per serving of RTE products obtained under these scenarios was then compared with the risk estimated in the baseline condition. Some risk mitigations had a consistent impact on the predicted listeriosis risk in all baseline conditions (e.g. presence or absence of growth inhibitor), whereas others were greatly dependent on the initial baseline conditions or practices in the deli (e.g. preslicing of products). Overall, the control of the bacterial growth and the control of contamination at its source were major factors of listeriosis risk in these settings. Although control of cross-contamination and continued sanitation were also important, the decrease in the predicted risk was not amenable to a simple solution. Findings from these predictive scenario analyses are intended to encourage improvements to retail food safety practices and mitigation strategies to control L. monocytogenes in RTE foods more effectively and to demonstrate the utility of quantitative risk assessment models to inform risk management decisions.

Stakeholders in the public health risk analysis community can possess differing opinions about what is meant by \"conduct a risk assessment.\" In reality, there is no one-size-fits-all risk assessment that can address all public health issues, problems, and regulatory needs. Although several international and national organizations (e.g., Codex Alimentarius Commission, Office International des Epizooties, Food and Agricultural Organization, World Health Organization, National Research Council, and European Food Safety Authority) have addressed this issue, confusion remains. The type and complexity of a risk assessment must reflect the risk management needs to appropriately inform a regulatory or nonregulatory decision, i.e., a risk assessment is ideally \"fit for purpose\" and directly applicable to risk management issues of concern. Frequently however, there is a lack of understanding by those not completely familiar with risk assessment regarding the specific utility of different approaches for assessing public health risks. This unfamiliarity can unduly hamper the acceptance of risk assessment results by risk managers and may reduce the usefulness of such results for guiding public health policies, practices, and operations. Differences in interpretation of risk assessment terminology further complicate effective communication among risk assessors, risk managers, and stakeholders. This article provides an overview of the types of risk assessments commonly conducted, with examples primarily from the food and agricultural sectors, and a discussion of the utility and limitations of these specific approaches for assessing public health risks. Clarification of the risk management issues and corresponding risk assessment design needs during the formative stages of the risk analysis process is a key step for ensuring that the most appropriate assessment of risk is developed and used to guide risk management decisions.

Deli meat was ranked as the highest-risk ready-to-eat food vehicle of Listeria monocytogenes within the 2003 U.S. Food and Drug Administration and U.S. Department of Agriculture, Food Safety and Inspection Service risk assessment. The comparative risk of L. monocytogenes in retail-sliced versus prepackaged deli meats was evaluated with a modified version of this model. Other research has found that retail-sliced deli meats have both higher prevalence and levels of L. monocytogenes than have product sliced and packaged at the manufacturer level. The updated risk assessment model considered slicing location as well as the use of growth inhibitors. The per annum comparative risk ratio for the number of deaths from retail-sliced versus prepackaged deli meats was found to be 4.89, and the per-serving comparative risk ratio was 4.27. There was a significant interaction between the use of growth inhibitors and slicing location. Almost 70% of the estimated deaths occurred from retail-sliced product that did not possess a growth inhibitor. A sensitivity analysis, assessing the effect of the model's consumer storage time and shelf life assumptions, found that even if retail-sliced deli meats were stored for a quarter of the time prepackaged deli meats were stored, retail-sliced product is 1.7 times more likely to result in death from listeriosis. Sensitivity analysis also showed that the shelf life assumption had little effect on the comparative risk ratio.

The U.S. Department of Agriculture, Food Safety and Inspection Service is exploring quantitative risk assessment methodologies to incorporate the use of the Codex Alimentarius' newly adopted risk management metrics (e.g., food safety objectives and performance objectives). It is suggested that use of these metrics would more closely tie the results of quantitative microbial risk assessments (QMRAs) to public health outcomes. By estimating the food safety objective (the maximum frequency and/or concentration of a hazard in a food at the time of consumption) and the performance objective (the maximum frequency and/or concentration of a hazard in a food at a specified step in the food chain before the time of consumption), risk managers will have a better understanding of the appropriate level of protection (ALOP) from microbial hazards for public health protection. We here demonstrate a general methodology that allows identification of an ALOP and evaluation of corresponding metrics at appropriate points in the food chain. It requires a two-dimensional probabilistic risk assessment, the example used being the Monte Carlo QMRA for Clostridium perfringens in ready-to eat and partially cooked meat and poultry products, with minor modifications to evaluate and abstract required measures. For demonstration purposes, the QMRA model was applied specifically to hot dogs produced and consumed in the United States. Evaluation of the cumulative uncertainty distribution for illness rate allows a specification of an ALOP that, with defined confidence, corresponds to current industry practices.

The Interagency Risk Assessment-Listeria monocytogenes (Lm) in Retail Delicatessens provides a scientific assessment of the risk of listeriosis associated with the consumption of ready-to-eat (RTE) foods commonly prepared and sold in the delicatessen (deli) of a retail food store. The quantitative risk assessment (QRA) model simulates the behavior of retail employees in a deli department and tracks the Lm potentially present in this environment and in the food. Bacterial growth, bacterial inactivation (following washing and sanitizing actions), and cross-contamination (from object to object, from food to object, or from object to food) are evaluated through a discrete event modeling approach. The QRA evaluates the risk per serving of deli-prepared RTE food for the susceptible and general population, using a dose-response model from the literature. This QRA considers six separate retail baseline conditions and provides information on the predicted risk of listeriosis for each. Among the baseline conditions considered, the model predicts that (i) retail delis without an environmental source of Lm (such as niches), retail delis without niches that do apply temperature control, and retail delis with niches that do apply temperature control lead to lower predicted risk of listeriosis relative to retail delis with niches and (ii) retail delis with incoming RTE foods that are contaminated with Lm lead to higher predicted risk of listeriosis, directly or through cross-contamination, whether the contaminated incoming product supports growth or not. The risk assessment predicts that listeriosis cases associated with retail delicatessens result from a sequence of key events: (i) the contaminated RTE food supports Lm growth; (ii) improper retail and/or consumer storage temperature or handling results in the growth of Lm on the RTE food; and (iii) the consumer of this RTE food is susceptible to listeriosis. The risk assessment model, therefore, predicts that cross-contamination with Lm at retail predominantly results in sporadic cases.

Ready-to-eat (RTE) meat and poultry product samples collected between 2005 and 2017 from RTE-producing establishments for the U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) ALLRTE/RTEPROD_RAND (random) and RTE001/RTEPROD_RISK (risk-based) sampling projects were tested for Listeria monocytogenes (Lm). Data for 45,897 ALLRTE/RTEPROD_RAND samples collected from 3,607 distinct establishments and 112,347 RTE001/RTEPROD_RISK samples collected from 3,283 distinct establishments were analyzed for the presence of Lm. These data were also analyzed based upon the percentages of establishments with positive samples, annual production volume, sanitation control alternatives, geographic location, and season or month of sample collection. Results revealed low occurrence of Lm-positive samples from the random and risk-based sampling projects, with 152 (0.33%) positive samples for ALLRTE/RTEPROD_RAND and 403 (0.36%) positive samples for RTE001/RTEPROD_RISK. The percentage of positive samples significantly decreased over time, from about 0.7% in 2005 and 2006 to about 0.2% in 2017 (P < 0.05). From 2005 to 2017, 3.9% of establishments sampled under the ALLRTE/RTEPROD_RAND sampling project had at least one Lm-positive sample. Similarly, 10.0% of establishments sampled under the RTE001/RTEPROD_RISK sampling project had at least one positive sample. Samples positive for Lm were found in all geographic regions in all months. Thus, in 13 years of RTE product sampling in FSIS-regulated establishments (2005 through 2017), <0.4% of samples were positive for Lm in both risk-based and random sampling projects. The low prevalence of Lm in these products suggests that the combination of FSIS policies and industry practices may be effective for controlling Lm contamination. Information obtained from these sampling projects is relevant to the ongoing prevention of foodborne Lm illnesses from RTE meat and poultry products.

Ready-to-eat (RTE) deli meats are considered a food at high risk for causing foodborne illness. Deli meats are listed as the highest risk RTE food vehicle for Listeria monocytogenes. Cross-contamination in the retail deli market may contribute to spread of pathogens to deli meats. Understanding potential cross-contamination pathways is essential for reducing the risk of contaminating various products. The objective of this study was to track cross-contamination pathways through a mock retail deli market using an abiotic surrogate, GloGerm, to visually represent how pathogens may spread through the deli environment via direct contact with food surfaces. Six contamination origination sites (slicer blade, meat chub, floor drain, preparation table, employee's glove, and employee's hands) were evaluated separately. Each site was inoculated with 20 ml of GloGerm, and a series of standard deli operations were completed (approximately 10 min of work). Photographs were then taken under UV illumination to visualize spread of GloGerm throughout the deli. A sensory panel evaluated the levels of contamination on the resulting contaminated surfaces. Five of the six contamination origination sites were associated with transfer of GloGerm to the deli case door handle, slicer blade, meat chub, preparation table, and the employee's gloves. Additional locations became contaminated (i.e., deli case shelf, prep table sink, and glove box), but this contamination was not consistent across all trials. Contamination did not spread from the floor drain to any food contact surfaces. The findings of this study reinforce the need for consistent equipment cleaning and food safety practices among deli workers to minimize cross-contamination.