Putting Principles into Practice:

Useful Case Studies

701 13th Street, N.W., Suite 750, Washington, DC, 20005, USA

E-mail: amokhtari@rti.org Phone: (202) 728-1973 Fax: (202) 728-2095

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

Model Results

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 log10 hand washing efficiency, hand washing compliance of 80% was required to limit the contamination level below the critical level

• High inactivation efficiency (3 log10) 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 log10 (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)