Progress 09/15/00 to 09/14/03
Outputs
The goal of this project was to integrate research, outreach, and teaching efforts to develop, evaluate and deliver science-based control programs for L. monocytogenes in the food industry. We selected 10 seafood processing plants (4 smoked fish plants, 4 crab plants, 2 crawfish plants) in various US states to participate in this study. All 10 plants were observed over an initial year or harvest season to determine Listeria contamination patterns. For each plant, 12-14 environmental, 6 raw material, and 6 finished product samples were collected 8-12 times throughout the processing season. L. monocytogenes raw material contamination rates varied from 0-10 pct for smoked fish and from 0-4.2 pct for crawfish. Only 3 out of 312 finished product samples were positive for L. monocytogenes. The incidence of L. monocytogenes in environmental samples varied from 0-30 pct, with drains (0-57 pct) and employee contact surfaces (gloves, aprons, and door handles) showed the highest
contamination rates (0-21 pct). L. monocytogenes subtype analysis allowed us to define persistent contamination with specific L. monocytogenes in three processing plants. Based on these initial results, plant-specific Listeria control strategies and employee training programs were developed and implemented. Listeria spp. prevalence in raw crawfish varied significantly from one season to another. However, the increased contamination prevalence for raw materials observed in the year after implementation of interventions strategies only resulted in a limited Listeria prevalence increase for the processing plant environment with extremely low levels of finished product contamination. Heat treatment of raw materials combined with Listeria control strategies to prevent cross contamination appear to be effective in achieving low levels of finished product contamination, even with Listeria spp. prevalences for raw crawfish of greather than 50 pct. Data for the smoked fish plants showed
significant reductions in the prevalence of environmental Listeria spp. contamination for non-food contact surfaces and overall core environmental samples. Listeria prevalence in environmental samples remained similar in floor drains before and after intervention strategies (49.6 and 54.2 pct, respectively). While there was an initial correlation between prevalence of L. monocytogenes in the environment and prevalence in finished products, after implementation of intervention strategies environmental prevalence of L. monocytogenes had reduced predictability for finished product contamination. Molecular subtyping showed that specific L. monocytogenes ribotypes persisted in 3 processing plants. A few persistent subtypes were responsible for finished product contamination events. Ribotype data also indicated that incoming raw material was only rarely a direct source of finished product contamination. While our data indicated that employee training in combination with targeted,
plant-specific Listeria intervention strategies can reduce cross contamination and Listeria spp. and L. monocytogenes prevalence in the plant environment, elimination of persistent L. monocytogenes strains remains a challenge.
Impacts
The intervention strategies developed this project will provide science-based materials and training programs, which can be used by the food industry to better control Listeria monocytogenes contamination in the processing environment and of finished products. Intense employee training and improved control strategies can lead to a lower number of contaminated food products and thus to a reduction of foodborne Listeria monocytogenes infections.
Publications
- Hoffman, A., K. Gall, D. Norton, and M. Wiedmann. 2003. Listeria monocytogenes contamination patterns for the smoked fish processing environment and for raw fish. J. Food Prot. 66:52-60
- Thimothe, J., K. Kerr Nightingale, K. Gall, V. N. Scott, and M. Wiedmann. 2004. Tracking of Listeria monocytogenes in smoked fish processing plants. J. Food. Prot. (in press)
- Lappi, V. R., J. Thimothe, J. Walker, J. Bell, K. Gall, M. W. Moody, and M. Wiedmann. 2004. Impact of Intervention Strategies on Listeria Contamination Patterns in Crawfish Processing Plants: A Longitudinal Study. J. Food. Prot. (accepted 01/05/2004; JFP 03-311)
- Lappi, V. R., A. Ho, K. Gall, and M. Wiedmann. 2004. Prevalence and growth of Listeria on naturally contaminated smoked salmon over 28 days of storage at 4 C. J. Food. Prot. (accepted 01/04/2004)
- Gall, K., V. N. Scott, R. Collette, M. Jahncke, D. Hicks, and M. Wiedmann. 2003. Listeria controls for smoked seafood: Implementing targeted GMP and sanitation procedures to prevent finished product contamination. Trends in Food Protection (accepted 01/05/2004)
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Progress 01/01/02 to 12/31/02
Outputs
The goal of this project is to integrate research, outreach, and teaching efforts to develop, evaluate and deliver science-based control programs for L. monocytogenes in the food industry. Our hypothesis is that improved environmental control strategies and sanitation procedures will significantly reduce L. monocytogenes contamination of Ready-To-Eat (RTE) food products. One additional goal of this project is to develop and apply molecular subtyping ('DNA fingerprinting') methods to accurately track the sources and spread of Listeria contamination in food processing plants. We have selected 10 RTE seafood processing plants (4 smoked fish plants, 4 crab plants, 2 crawfish plants) in various US states to participate in this study. All 10 plants were observed over an initial year or harvest season to determine Listeria contamination patterns. A questionnaire was used to assess management factors in each participating plant, which may affect Listeria contamination
patterns and sources. For each plant, 12 - 14 environmental samples, 6 raw material samples and 6 finished product samples were collected 8 - 12 times throughout the processing season. Samples were tested for L. monocytogenes and for Listeria spp. Our initial results showed L. monocytogenes raw material contamination rates varied from 0-10 percent for smoked fish and from 0 - 4.2 percent for crawfish. Only 3 out of 312 finished product samples (smoked fish and crawfish) were positive for L. monocytogenes. The incidence of L. monocytogenes in environmental samples varied from 0 - 30 percent, with drains (0-57 percent) and employee contact surfaces (0-21 percent) showing the highest contamination rates. Employee contact surfaces included gloves, aprons, and door handles. L. monocytogenes isolates were characterized by molecular subtyping to further define contamination patterns. Subtype analysis allowed us to define persistent contamination with specific L. monocytogenes in three
processing plants. Based on these initial results, plant-specific Listeria control strategies and employee training programs were developed and implemented. Preliminary analysis of data, pre- and post intervention, for the four smoked fish processing plants showed minor reductions in L. monocytogenes contamination of raw, finished and environmental samples. Food contact surfaces showed the most significant decrease in contamination levels, with a p-value = 0.177. In additional preliminary statistical analysis, two of the four smoked fish plants showed a statistically significant decrease of L. monocytogenes contamination in at least one environmental sampling category (food contact surface, non-food contact surface, and/or drains). In conclusion, our data indicates that targeted interventions strategies and employee training can contribute to a decrease in L. monocytogenes contamination in an individual smoked fish processing plant. Additional long-term in-plant studies will be needed
to further develop and verify effective in-plant Listeria intervention strategies.
Impacts
The intervention strategies developed this project will provide science-based materials and training programs, which can be used by the food industry to better control Listeria monocytogenes contamination in the processing environment and of finished products. Intense employee training and improved control strategies can lead to a lower number of contaminated food products and thus to a reduction of foodborne Listeria monocytogenes infections.
Publications
- Thimothe, J., J. Walker, V. Suvanich, K. L. Gall, M. W. Moody, and M. Wiedmann. 2002. Detection of Listeria in crawfish processing plants and in raw, whole crawfish and processed crawfish (Procambarus spp.). J. Food Prot. 65: 1735-1739.
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Progress 01/01/01 to 12/31/01
Outputs
The goal of this project is to integrate research, outreach, and teaching efforts to develop, evaluate and deliver science-based control programs for L. monocytogenes in the food industry. Our hypothesis is that improved environmental control strategies and sanitation procedures will significantly reduce L. monocytogenes contamination of RTE food products. One additional goal of this project is to develop and apply molecular subtyping (?DNA fingerprinting?) methods to accurately track the sources and spread of Listeria contamination in food processing plants. We have selected 10 RTE seafood processing plants (4 smoked fish plants, 4 crab plants, 2 crawfish plants) in various US states to participate in this study. All 10 plants were used to determine Listeria contamination patterns for an initial year or season. A questionnaire was used to assess management factors in the participating plants, which may affect Listeria contamination patterns and sources. For each
plant, 12 ? 14 environmental samples, 6 raw material samples and 6 finished product samples were collected 8 ? 12 times throughout the processing season. Samples were tested for L. monocytogenes and for Listeria spp. L. monocytogenes raw material contamination rates varied from 0-10% for salmon and from 0 ? 4.2% for crab and crawfish. Only 3 out of 429 finished products were positive for L. monocytogenes. The incidence of L. monocytogenes in environmental samples varied from 0 ? 28% with drains (0-57%) and employee contact surfaces (0-21%) showing the highest contamination rates. Employee contact surfaces included gloves, aprons, and door handles. L. monocytogenes isolates were also characterized by molecular subtyping to further define contamination patterns. Subtype analysis allowed us to define persistent contamination with a specific L. monocytogenes in three processing plants. Persistence was limited to the raw product area in one plant and to the processing area in another
plant. In the third plant, persistent subtypes were present throughout the processing environment. Based on our initial results we have developed recommendations for Listeria control strategies, which will be implemented in the participating plants in Year 2 of our project. We have also developed a Listeria control manual and a employee training program, which we will test in Year 2 of this project. These materials have already been reviewed by the project team, which includes members from academia and industry, and will be used in project year 2
Impacts
This project will provide science-based materials and training programs, which can be used by the food industry to better control Listeria monocytogenes contamination in the processing environment and of finished products. Improved control strategies will lead to a lower number of contaminated food products and thus to a reduction of foodborne Listeria monocytogenes infections.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
Listeria monocytogenes is a bacterium that is transmitted through contaminated foods. Annually, foodborne Listeria infections cause an estimated 2,500 disease cases and 500 deaths in the US. L. monocytogenes is commonly found in food processing plant environments and most contamination of ready-to-eat (RTE) foods appears to originate from the food processing plant environment. The goal of this project is to integrate research, outreach, and teaching efforts to develop, evaluate and deliver science-based control programs for L. monocytogenes in the food industry. Our hypothesis is that improved environmental control strategies and sanitation procedures will significantly reduce L. monocytogenes contamination of RTE food products. One additional goal of this project is to develop and apply molecular subtyping ("DNA fingerprinting") methods to accurately track the sources and spread of Listeria contamination in food processing plants. We are working with the RTE seafood
industry as model system to develop intervention and control strategies for L. monocytogenes. We have selected 10 RTE seafood processing plants in various US states, which will participate in this study. A questionnaire has been developed to assess management factors in the participating plants, which may affect Listeria contamination patterns and sources. Preliminary data, which have been collected to determine the most appropriate in-plant sampling sites, indicate that inclusion of drains in sampling plans may provide an appropriate strategy to probe for L. monocytogenes subtypes that persist in the plant environment. In the next stage of this project we will collect environmental samples from participating plants, which will be tested for the presence of Listeria species and L. monocytogenes. Isolates will be subtyped using DNA-based subtyping methods to characterize contamination patterns. Initial results from participating plants will be used to develop environmental Listeria
control strategies and monitor their effects on contamination patterns and frequencies in these plants. Data form the test plants will then be used to develop outreach and training programs to communicate and broadly implement recommended Listeria control strategies.
Impacts
The outcome of this project will be a better control of Listeria monocytogenes contamination, which will results in a lower number of contaminated food products and thus in a reduction of foodborne Listeria monocytogenes infections.
Publications
- No publications reported this period
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