Presentation on theme: "Putting Principles into Practice: Useful Case Studies 701 13 th Street, N.W., Suite 750, Washington, DC, 20005, USA"— Presentation transcript:
Putting Principles into Practice: Useful Case Studies th Street, N.W., Suite 750, Washington, DC, 20005, USA Phone: (202) Fax: (202) Dubai International Food Safety Conference, February 24-26, 2009 Dubai, UAE Amir Mokhtari, Ph.D.
We are going to talk about… Challenges facing food safety authorities What we mean by risk analysis How risk analysis can be used How risk analysis can improve decisions Microbial risk assessment (MRA) and food safety MRA Case Study #1: L. monocytogenes MRA Case Study #2: Norovirus transmission Concluding remarks
What are the challenges facing food safety authorities? Rapidly growing volume and diversity of food trade Changing agricultural practices, production and manufacturing systems, food handling patterns, etc. New and emerging food-borne hazards Effect of climate change on the food supply New food and agricultural technologies Greater public demands for health protection Requirements of sanitary and phyto-sanitary measures to be based on science and risk assessment
What is risk analysis? Risk assessment- science-based tasks of measuring and describing the nature of the risk being analyzed Risk management- defines the problem, articulates the goals of the risk analysis and identifies questions to be answered Risk communication- interactive exchange of information among risk managers, risk assessors, consumers and other stakeholders
How is risk analysis used? To predict the likelihood of exposure to harmful agents that result in an adverse human health outcome To prioritize food-related threats to public health in support of the decision-making process (e.g., resource allocation) To identify points along the food supply chain that contribute to the public health risk To evaluate and rank mitigation options and strategies with respect to human health outcomes To provide the scientific and technical basis needed to develop risk management strategies To communicate with stakeholders about the risks and measures applied
How does risk analysis improve the decision-making process? Support decisions that are in proportion to public health risks involved Enable systematic evaluation of likely impacts of measures selected to manage risks Allow likely costs of compliance to be compared with expected benefits Provide a useful metric in prioritizing different food safety problems Meet obligations under international agreements and enhance trades Identify gaps and uncertainties in scientific knowledge to help set research priorities
Microbial risk assessment (MRA) and food safety MRA is performed for pathogen/food combinations that may be associated with food-borne illness (single pathogen, one product, the entire supply chain)
Basic Components of an MRA
Microbial risk assessment covers the farm-to-fork continuum Microbiological Risk Assessment can be applied to each individual step in a (typical) food supply chain, from primary production to consumption (single pathogen, one product, all supply chains)
MRA Case Study #1: L. monocytogenes in Deli Meats FDA/USDA examined the effectiveness of testing and sanitation of food contact surfaces to reduce product contamination and risk of illness Provided guidance on how frequently to test and sanitize food contact surfaces for Listeria spp.
FDA used MRA to rank LM risks of Ready-to-Eat (RTE) products Approach: relative risk ranking of food categories Purpose: identify the food category with the greatest public health risk Key finding: deli meats pose the highest risk, and hence, deserve the focus
MRA Model Applied to the High Risk Category – Deli Meats An “in-plant” model that predicts LM concentrations at retail Coupled with an updated version of the FDA Listeria model to predict human health impacts Track bacteria as they move from one media to another Incorporates FCS testing, product testing, sanitation, pre- and post-packaging interventions, growth inhibitors, etc.
MRA Model Provided Important Information on Interventions Positive food contact surfaces for Listeria species greatly increased the likelihood of finding positive RTE product lots Minimal testing frequency of food contact surfaces will only result in a small reduction in the levels of contamination at retail Increased frequency of food contact surface testing and sanitation can reduce the risk of listeriosis Combinations of interventions appear to be much more effective than any single intervention
Based on the MRA, Alternatives Were Developed to Reduce Risk Alternative 1 – Employ both a post-lethality treatment and a growth inhibitor for Listeria on RTE products. Establishments opting for this alternative will be subject to FSIS verification activity that focuses on the post-lethality treatment effectiveness. Alternative 2 – Employ either a post-lethality treatment or a growth inhibitor for Listeria on RTE products. Establishments opting for this alternative will be subject to more frequent FSIS verification activity than for Alternative 1. Alternative 3 – Employ sanitation measures only. Establishments opting for this alternative will be targeted with the most frequent level of FSIS verification activity.
Case Study #2: Transmission of Noroviruses by food handlers Leading cause of food borne disease Poor handling practices of infected food handlers are responsible for the majority of infection cases No available study on the behavior of human noroviruses in food preparation environments No available systematic MRA exercise with a focus on poor handling practices
Designed a MRA with Specific Management-Related Goals in Mind Investigate the behavior of enteric viruses in the food preparation environment Investigate the role of poor personal hygiene in transmission of enteric viruses Incorporate the behavioral factors to evaluate control strategies aimed at food handling
How virus particles are transferred in a food preparation environment
Representing reality using a mathematical model
Considered Scenarios that were Relevant to Control Strategies Changes in: Employee’s behavior Sanitation practices Persistence and inactivation of virus particles Cross-contamination sources: Hands and gloves of an employee Food contact surfaces Time component: Food preparation Sanitation practices Visiting bathroom
Hand washing versus gloving: which one is a more effective way to control risk? Even with 100% hand washing compliance, at least 30% gloving is required to limit the contamination level below the critical level With observed hand washing compliance in food establishments (e.g., ~60%), at least 65% gloving compliance is required to limit the contamination level below the critical level Critical Level: minimum number of viral particles that is sufficient to infect an individual
Hand washing efficiency versus hand washing compliance: which one is more important? Critical Level: minimum number of viral particles that is sufficient to infect an individual Even with 3 log 10 hand washing efficiency, hand washing compliance of 80% was required to limit the contamination level below the critical level High inactivation efficiency (3 log 10 ) could not entirely ensure product safety given the observed hand washing compliance in food establishments (i.e., <60%) With 100% compliance, inactivation rate of approximately 0.7 log 10 (i.e., 80%) still required
Fecal contamination versus restroom contamination Frequent cleaning of the restroom environment is an effective way to control the transmission of Norovirus particles to food products Low environmental contamination ensured up to 95% of food products with contamination levels less than the critical level In contrast, food products were highly contaminated for scenarios in which the restroom environment was highly contaminated Critical Level: minimum number of viral particles that is sufficient to infect an individual
MRA Model Provided Important Information on Control Strategies NoV show persistence on environmental surfaces (and hands) and are transferred with relative ease Current alcohol-based hand sanitizers (70%) do not appear efficacious for control of the NoV Even with less than perfect data, a preliminary exposure model for the transmission of NoV in the food preparation environment was feasible The model is most sensitive to factors impact degree of virus shedding and to food handler behaviors There is an important interplay between compliance with recommended hygiene practices and virus removal (inactivation) efficiency
Concluding Remarks Risk assessment is a powerful tool for evaluating strategies to reduce disease and for prioritizing future research needs Because we can not “inspect our way to food safety,” risk assessment should be an integral part of food safety policy Scientists, risk managers, and policy makers need to work together to develop a food safety system that is both responsive and proactive in addressing threats to our food supply
Acknowledgements Collaborators Steve Beaulieu (RTI International) Dr Lee-Ann Jaykus (North Carolina State University) Dr. Christine Moe (Emory University) Dr. Jan Vinje (CDC)