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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL MODELING AND BIOINFORMATICS FOR FOOD SAFETY AND SECURITY

Location: Residue Chemistry and Predictive Microbiology

2008 Annual Report


1a.Objectives (from AD-416)
To evaluate, validate, and where necessary, develop new innovative, robust and valid predictive models for the responses of microbial pathogens, including foodborne threat agents, in select food matrices, as a function of: temperature, food formulation, competitive microflora, physiological history, and surface transfer. To develop novel approaches to assess model performance and robustness, leading to more efficient strategies for producing and extrapolating models to different classes of food. To determine the probability distribution of lag phase duration (LPD) for foodborne pathogens, as a function of the previous bacterial physiological history, to allow risk managers to estimate worst-and best-case scenarios for pathogen behavior, depending on likely sources of contamination; To identify molecular markers that discriminate bacterial lag, growth and stationary phases, thus leading to more mechanistic models and greater certainty for LPD prediction.


1b.Approach (from AD-416)
Quantitative data will be collected for the effects of selected environmental parameters on foodborne pathogen growth, survival and inactivation. Relevant environmental conditions will include food formulation, native microbial flora, inoculum level, bacterial history, and the effects of food process operations. Priority pathogen-food combinations will be identified through stakeholder interactions and by identifying sensitive data gaps in microbial risk assessment. Experimental data will be used to confirm and where necessary produce primary growth and inactivation models, as well as probabilistic models for growth/no growth interfaces and microbial transfer among food processing surfaces. Model performance will be described using independent validation data from ongoing experiments with food matrices and microbiology databases such as ComBase. The resulting technologies will be transferred to stakeholders vis the ARS Pathogen Modeling Program and process risk model software.


3.Progress Report
The research is relevant to Component 1.2 (Pathogen Reduction Postharvest) in the 2006-2010 NP 108 Action Plan. We defined the heat treatment (55-73.9C) required to achieve a specified lethality for E. coli O157:H7 in ground beef. The thermal death predictive model for the pathogen, which can predict D-values for any combinations of the factors that are within the range of those tested, was developed. Using these inactivation kinetics or predictive model for E. coli O157:H7, food processors can design thermal processes for the production of a safe beef product with extended shelf life.

The research is relevant to Component 1.2 (Pathogen Reduction Postharvest) in the 2006-2010 NP 108 Action Plan. In collaboration with University of Maryland, Eastern Shore (UMES) faculty and students completed a survey of Salmonella strains in a commercial processing plant including characterization of the strains for antimicrobial resistance patterns. Selected strains from this study will be used in future modeling studies to investigate, characterize and model strain variation effects on Salmonella growth and survival on poultry during processing, distribution, handling and storage.

The research is relevant to Component 1.2 (Pathogen Reduction Postharvest) in the 2006-2010 NP 108 Action Plan. In collaboration with UMES faculty and students, characterized the growth and survival kinetics of Listeria monocytogenes in broth culture as a function of temperature, pH and sodium lactate/diacetate levels. The data will be used to develop and validate a predictive model for growth and survival of Listeria monoctyogenes in ready-to-eat foods.

The research is relevant to Component 1.2 (Pathogen Reduction Postharvest) in the 2006-2010 NP 108 Action Plan. Developed and validated a model for growth of Salmonella Typhimurium DT104 from a low initial dose on chicken frankfurters with native microflora. This is the first model for growth of any strain of Salmonella on a ready-to-eat meat product with native microflora. Growth of Salmonella on chicken frankfurters was restricted by the native micro-flora and food formulation, which contained multiple anti-microbial compounds. Thus, the model will benefit the poultry industry by providing predictions that do not over-estimate the risk of Salmonella growth and infection compared to exiting models developed in sterile food systems.


4.Accomplishments
1. Safe time/temperature for cooling of cooked foods. Improper storage and/or inadequate cooling practices in retail food operations have been cited as the cause of food poisoning for 97% of Clostridium perfringens outbreaks. Mathematical models were developed to predict the relative growth of C. perfringens from spores at temperatures applicable to the cooling of cooked uncured pork. The growth data /predictive models on the safe cooling rate of meat will enable the food industry to assure that cooked products remain pathogen-free. The research is relevant to Component 1.2 (Pathogen Reduction Postharvest), Problem Statement 1.2.7 (Risk Assessment), in the 2006-2010 NP 108 Action Plan.

2. Thermal inactivation of foodborne pathogens. Insufficient lethality of thermal treatments is believed to be the primary contributing factor in outbreaks associated with the consumption of meat and poultry products. We defined the heat treatment (55-73.9C) required to achieve a specified lethality for E. coli O157:H7 in ground beef. The thermal death predictive model for the pathogen, which can predict D-values for any combinations of the factors that are within the range of those tested, was developed. Using these inactivation kinetics or predictive model for E. coli O157:H7, food processors can design thermal processes for the production of a safe beef product with extended shelf life. The research is relevant to Component 1.2 (Pathogen Reduction Postharvest), Problem Statement 1.2.7 (Risk Assessment) and 1.2.9 (Food Security), in the 2006-2010 NP 108 Action Plan.

3. The use of raw meat in the manufacturing of fermented dry and semidry sausage may introduce L. monocytogenes, Escherichia coli O157:H7 and Salmonella spp into the finished product. Understanding the survivability of these pathogens in sausage during the manufacturing processes allows processing/product parameters to be selected to minimize the presence of the pathogens in finished products. Studies conducted to collect the inactivation data of L. monocytogenes, E. coli O157:H7 and S. typhymurium in sausage were completed. Models describing the rates of inactivation of these pathogens in fermented sausage during fermentation, drying, and storage were developed. The models are particular useful for small and very small fermented sausage producers to identify product formulation and processing/handling conditions that ensure the safety of their products. The research is relevant to Component 1.2 (Pathogen Reduction Postharvest), Problem Statement 1.2.7 (Risk Assessment), in the 2006-2010 NP 108 Action Plan.

4. Impact of the blade surface texture on pathogen surface transfer during mechanical slicing of deli meats. Food safety managers currently lack the ability to predict the microbial pathogen transfer in slicing operation for ready-to-eat foods. The surface roughness likely to affect the transfer of pathogens was measured by the Confocal Laser Scanning Microscopy (CLSM) in terms of two parameters, namely, arithmetic average of the profile ordinates along a line segment (Ra) and surface ratio (Rs) within a region of interest (ROI) of the CLSM images (3-D topographies). Our findings suggest that the surface roughness significantly affects the pathogen attachment or adhesion on blade surface. This, in turn, further affects the microbial surface transfer during slicing operations. By understanding the surface transfer, the production or retail (Franchise) equipment and operations for RTE deli meat may be further improved and therefore, reduce the possibility of outbreaks. The surface texture parameters will be incorporated into the model development in the future studies. Finally, the models will be available through the PMP and ComBase. The research is relevant to Component 1.2 (Pathogen Reduction Postharvest), Problem Statement 1.2.7 (Risk Assessment), in the 2006-2010 NP 108 Action Plan.

5. Model for growth and survival of Salmonella on chicken skin. Salmonella is a leading cause of human illness and is often found associated with the skin of chicken. However, little is known about the ability of Salmonella to survive and grow on chicken skin during retail sale and home storage. Therefore, research was conducted that resulted in the development and validation of a model that predicts the survival and growth of Salmonella from low to high levels on chicken skin stored under conditions found in the retail store and consumer home. The model will help regulators and poultry companies more accurately predict and control the risk of Salmonella infection from contaminated chicken that has been improperly handled before consumption. This research contributes to accomplishment of Problem Statement 1.2.7 Risk [Assessment] in the ARS, National Program 108 – Food Safety.

6. Growth model and plasmid stability of Yersinia pseudotuberculosis in ground beef. The potential growth of virulence plasmid-bearing YPST at refrigerated temperatures could pose an increased health risk for contaminated retail RGB if commercial and consumer storage is extended for a longer period such as 4 to 6 weeks. Therefore, a growth model of plasmid-bearing Yersinia pseudotuberculosis (YPST) in ground beef was developed. The potentially unstable virulence-associated plasmid was retained in YPST during its growth in ground beef and therefore, beef contaminated with YPST could cause disease due to refrigeration failure, temperature (10-25 degrees C) abuse, or if the meat was not properly cooked. Since the chromosomal DNA sequence of Y. pestis and YPST are nearly identical, the model developed can be used for as a reference for Y. pestis growth in ground beef and therefore, ensure safety of the food. This will assist the government risk assessors and food companies for predicting the fate of YPST and Y. pestis where bulk foods could be contaminated, thereby exposing a relatively large number of individuals and thus improve exposure assessment and aid in designing more effective food safety controls. The research is relevant to Component 1.2 (Pathogen Reduction Postharvest), Problem Statement 1.2.7 (Risk Assessment) and 1.2.9 (Food Security), in the 2006-2010 NP 108 Action Plan.


5.Significant Activities that Support Special Target Populations
Collaborated with a small producer of fermented sausage named Mediterranean Foods, a company with 2 employees and an annual sale of less than $200,000, located in Upper Darby, Pennsylvania, to examine the behavior of E. coli O157:H7, Salmonella, and L. monocytogenes on fermented, semi-dry sausage introduced by post-processing contamination. The producer provides finished commercial products, and ARS conducts the challenge study.

Three minority students were hired and assisted in this research as part of the ARS/1890 Center of Excellence at the University of Maryland Eastern Shore. The Center of Excellence was established to promote interest among minorities for pursuing advanced careers in agriculture research and to strengthen the relationship between USDA and 1890 Institutions.


6.Technology Transfer

Number of the New MTAs (providing only)2
Number of Web Sites Managed3

Review Publications
Hwang, C., Tamplin, M. 2007. Modeling the Lag Phase and Growth Rate of Listeria monocytogenes in Ground Ham Containing Sodium Lactate and Sodium Diacetate at Various Storage Temperatures. Journal of Food Science and Technology. 72(7):M246-M253.

Juneja, V.K., Sheen, S., Tewari, G. 2007. Intervention technologies for food safety and preservation. In: Wilson, C.L. editor. Microbial Food Contamination. 2nd edition. CRC Press. Ames, Iowa. p. 347-393.

Juneja, V.K., Marks, H., Thippareddi, H.H. 2007. Predictive model for growth of clostridium perfringens during cooling of cooked uncured beef. Food Microbiology. 25:42-55.

Juneja, V.K. 2007. Thermal inactivation of salmonella spp. in chicken as affected by ph of the meat. International Journal of Food Science and Technology. 42:1443-1448.

Hoque, M.M., Inatsu, M.B., Juneja, V.K., Kawamoto, S. 2007. Antibacterial activity of guava (psidium guajava l.) and neem (azadirachta indica a. juss.)extracts against food borne pathogens and spoilage bacteria. Foodborne Pathogens & Disease. 4:481-488.

Velugoti, P.R., Rajagopal, L., Juneja, V.K., Thippareddi, H. 2007. Use of Calcium, Potassium, and Sodium Lactates to Control Germination and Outgrowth of Clostridium perfringens Spores during Chilling of Injected Pork. Food Microbiology. 24(7-8):687-694.

Aarnisalo, K., Sheen, S., Raaska, L., Tamplin, M. 2007. Modelling transfer of listeria monocytogenes during slicing of "gravad" salmon. International Journal of Food Microbiology. 118(1):69-78.

Sheen, S., Hwang, C. 2008. Modeling Transfer of Listeria monocytogenes on Deli Meat During Mechanical Slicing. Foodborne Pathogens and Disease. 5(2):135-146.

Hwang, C. 2007. The Effect of Salt, Smoke Compound, and Storage Temperature on the Growth of Listeria monocytogenes in Simulated Smoked Salmon. Journal of Food Protection. 70:2321-2328.

Parveen, S., Taabodi, M., Mohamed, T., Schwarz, J.P., Oscar, T.P., Harter-Dennis, J., Hubert, S., White, D. 2007. Prevalence and Antimicrobial Resistance of Salmonella spp. Recovered from Processed Poultry. Journal of Food Protection. 70(11):2466-2472.

Abou-Zeid, K.A., Yoon, K.S., Oscar, T.P., Schwarz, J.G., Hashem, F.M., Whiting, R.C. 2007. Survival and growth of Listeria monocytogenes in broth as a function of temperature, pH, and potassium lactate and sodium diacetate concentrations. Journal of Food Protection. 70(11):2620-2625.

Oscar, T.P. 2008. Predictive model for verification of critical control points for growth of salmonella typhimurium dt104 on chicken frankfurters after thermal processing. International Journal of Food Microbiology. 71(6):1135-1144.

Hoque, M.M., Inatsu, M.B., Juneja, V.K., Kawamoto, S. 2007. Antimicrobial Activity of Cloves and Cinnamon Extracts against Food Borne Pathogens and Spoilage bacteria, and Inactivation of Listeria monocytogenes in Ground Chicken meat with their Essential oils. National Food Research Institute's. 72:9-21.

Sheen, S., Bao, G., Cooke, P.H. 2008. Food surface texture measurement using reflective confocal laser scanning microscopy. Journal of Food Science and Technology. 73(5):227-234.

Last Modified: 7/28/2014
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