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December 2003
Since 1998, the Center for Food Safety and Applied Nutrition (CFSAN) has operated a competitive extramural research program. Through this program, CFSAN has been able to augment its food safety research and provide for critically needed research to develop the means to identify and characterize foodborne hazards more rapidly and accurately, to provide the tools for regulatory enforcement, and to develop effective interventions that can be used to prevent hazards at each step from production to consumption.
The extramural program supports novel collaborative research efforts between CFSAN and scientists and leverages expertise not found within CFSAN to complement and accelerate ongoing research. Collaborations such as these provide information critical to food safety guidance and policymaking, and stimulate fruitful interactions between FDA scientists and those within the greater research community.
This research is intended to help CFSAN achieve its research goals of reducing the incidence of foodborne illness and ensuring the integrity of foods, food additives, and dietary supplements.
Our mission is to reduce the incidence of foodborne illness to the greatest extent feasible. Research in food safety seeks to reduce the incidence of foodborne illness by improving our ability to detect and enumerate pathogens in the food supply and to find new ways to control them.
Prevention of foodborne pathogens in foods and the foodborne illness that can result requires an understanding of how foods become contaminated during their production, processing, and distribution, and the availability of practical interventions to control or eliminate the hazard.
Research in food safety seeks to reduce the incidence of foodborne illness by improving our ability to detect and quantitate foodborne pathogens, toxins, and chemicals that could jeopardize the safety and security of the food supply, and to find new and improved ways to control these agents.
Ensuring a safe food supply is difficult. New challenges such as increased variety of foods grown or produced in distant places, more meals eaten outside the home, new and more deadly pathogens, and an increasingly vulnerable population all contribute to the estimated 76 million foodborne illnesses each year, resulting in an estimated 325,000 hospitalizations and 5,000 deaths.
In fiscal year 2000, seven (7) grants totaling over $1,000,000 were funded:
What Have We Learned and Are We Closer to Eliminating and Reducing Illnesses?
Approximately 9.2 million cases of viral gastroenteritis caused by norovirus and over 4,000 cases of hepatitis A virus related to foodborne transmission of the virus (fresh produce, cake, deli meats, fruit salad, cheeses, and ice) during 2000 has been estimated (CDC, 2003). Unlike bacterial contaminants, viruses do not replicate on the food; however, the infectious dose for these agents is very small (1-100 virions). Only a small number of these pathogens may be present in a large volume of food and still cause infection. These viruses are not detectable using traditional culture methods.
The significant number of illnesses attributed to viruses underscores the need for a method that can detect viruses from a variety of food matrices. Through this grant, a method for the extraction of a virus from surface-contaminated food matrices and its detection by molecular technologies has been developed. The method is effective for detection of intentionally added virus from a variety of foods. Further work continues to detect and reduce inhibitory effects in the sample matrix.
Once refined, this method will provide the Agency with a tool that can be employed to detect foodborne viruses. The method will be useful in determining the cause of foodborne illnesses and in the development of preventive measures and programs.
Foodborne viral illness is a major public health concern. Norwalk-like viruses (NLVs), based on number of cases, and Hepatitis A virus (HAV), based on severity, are among the most important foodborne viruses. Although advances have been made in detecting viruses in foods, currently there is no standardized method suitable for routine monitoring and outbreak investigation. The general objective of this project is to develop and standardize an integrated framework of extraction, processing and molecular detection of NLVs and HAV suitable for routine monitoring and outbreak investigation in a variety of food commodities, including intact and minimally processed fruits and vegetables, shellfish, and other complex food items. This framework will be developed by evaluating existing, improved and new protocols and methods for each step of the process from extraction/elution through detection by RT-PCR. Elution and extraction methods will be compared for a variety of food commodities. A number of methods to remove inhibition from food extracts, including RNA extraction, PEG precipitation, spin column chromatography and antigen/RNA capture, will be evaluated for efficiency of inhibition removal as well as virus/RNA recovery. RT-PCR protocols will be optimized for a variety of food commodities, and a matrix of sensitive primers with broad detectability for HAV and NLVs will be chosen based on evaluation of existing primer sets against a panel of HAV and NLV isolates.
Through 2002 considerable effort has been applied towards developing and optimizing real-time RT-PCR primers and probes for the detection of HAV and NLV. These primers and probes, as well as internal positive controls for these viruses have been evaluated using tissue culture grown HAV, and stool derived NLVs. Progress has also been reported for the detection of these viruses in artificially contaminated food matrices such as pasta, tomato and lettuce. Final evaluation of the efficacy of these extraction and detection protocols will depend on the publication of these results in peer reviewed journals.
Outbreaks involving pathogenic microorganisms have been increasingly associated with fresh produce. In studying prevention for these types of outbreaks, it has been challenging to effectively reduce pathogens from produce surfaces using traditional sanitation treatments, such as chlorinated water washes. It is also difficult to interpret or compare efficacy data for pathogens after antimicrobial treatments due to the use of different experimental procedures and different model produce systems. In order to understand ideal sanitation procedures and better ensure the safety of produce, it is necessary to develop highly effective sanitizers and establish protocols to effectively evaluate the efficacy of different sanitation treatments.
To date, two main objectives have been studied. The first objective is to compare and standardize different inoculation procedures (i.e., dipping, spotting, and spraying) for three representative produce model systems (i.e., green pepper, lettuce, and strawberry). The second objective is to determine the effects of these inoculation methods on pathogen reduction (E. Coli O157:H7, L. monocytogenes, or Salmonella spp.) by treatment with chlorine dioxide (ClO2) gas and chlorinated water on each produce model system.
The study results suggested that bacterial recovery, attachment, and distribution were different for the three inoculation methods studied and for each of the three produce models. The efficacy data of ClO2 gas and chlorinated water treatments in reducing target pathogens on each type of produce were affected by different inoculation procedures and recovery methods. Under optimum conditions, ClO2 gas treatment resulted in more than a 5 log colony forming unit (cfu) reduction for selected pathogens on green pepper and strawberry surfaces while maintaining their quality. ClO2 gas exhibited much higher bactericidal effectiveness than chlorinated water wash (1-3 log cfu reduction). Although ClO2 gas treatment could achieve a more than 3 log reduction of bacteria on lettuce, discoloration of leaves was observed, indicating the limitation of ClO2 gas technology for lettuce. Further study indicates that cut produce and/or the amount of water present on produce surfaces has a great influence on lessening the antimicrobial effects of ClO2 gas treatments. Research supports that the preferred method of inoculation to achieve consistent and repeatable results is by spot inoculation. In controlled laboratory conditions, ClO2 gas treatment has shown promising results as a surface decontamination technique for pathogen reduction on whole produce (green pepper and strawberries) but was not successful on cut produce (lettuce). A pilot scale system is currently being constructed to evaluate the effectiveness of ClO2 gas technology for larger volumes of whole produce treated in a batch system. This system will be optimized for application treatments for several different types of produce.
If successful, this preventive measure could be used to reduce contamination of fresh produce and the number of foodborne illness associated with the consumption of fresh produce.
One possible source of contamination of fresh vegetables and fruits at the farms is contaminated water used to apply fungicides and pesticides. Recovery strategies of protozoan parasites using spot, spray, and dip spiking methodologies were investigated.
The effects of these chemicals on oocyst survival were examined. Study results suggest that Cyclospora oocysts are viable even up to 7 days post exposure at higher and lower doses than that recommended by the manufacturer. In conclusion, Cyclospora and Cryptosporidium oocysts are not affected by agricultural practices, and contaminated water can be a source of produce contamination.
The effects of temperature and different food matrices on sporulation and viability of Cyclospora cayetanensis was determined. Milk, diluted milk, and whipped cream were used as food substrates at refrigeration and freezing temperatures. No sporulation was observed at exposure time of 2 days or more. Refrigeration temperature (4° C) did not change the sporulation rate of Cyclospora in the dairy substrates. At 23° C, water, milk, diluted milk, and whipped cream proved to be a suitable substrate for oocysts to sporulate. Further study indicated that Cyclospora oocysts were resistant to high and low temperatures.
The Agency will use this important knowledge to develop preventive measures, recommendations, and strategies to prevent fresh vegetables and fruit from becoming contaminated with Cyclospora and to make recommendations to consumers regarding refrigeration and storage of fresh vegetables and fruits.
The goal of this project is to determine the food refrigeration knowledge and practices of consumers. During the first year of the project, eight focus groups were conducted in Tennessee. Outcomes of these focus groups were utilized in the formation of a survey instrument designed to collect quantifiable data from consumers regarding their knowledge of proper food handling, refrigeration practices, and other food safety issues. Trained interviewers completed a total of 551 questionnaires. The majority of respondents (85 percent) did not know what the temperature was of their refrigerator, and only 42 percent knew that it should be 40° F or below. Almost half (47 percent) said they had no idea what the temperature should be. Nineteen percent said that they had a thermometer in their refrigerator; however, half did not remember the last time they checked it. Non-food items reported as "stored in the refrigerator" included: Batteries, film, candles, tooth bleach, tickets, bird tallow, cigars, flowers, hosiery, lotions, nail polish, meal worms, and paint brushes.
A follow-up study was conducted in 210 homes to investigate the conditions under which refrigerated foods were stored. Temperature loggers, which record temperatures each minute, were placed in several sites within the refrigerators for 3 to 7 days. In some homes, a thermocouple was also placed in a refrigerated hot dog and a yogurt cup. Data assessment is in progress; thus, results are only preliminary. Mean temperatures within the refrigerators ranged from 35° F for the top shelf to 38° F on the bottom shelf. Five percent had average temperatures above 45° F, and 28 percent were above 40° F. The mean temperature on the door was 41.4° F; however, 65 percent had average temperatures above 40° F. The majority of the refrigerator doors (75 percent) were above 40° F for more than 6 hours per day. Of these, one-third were over 45° F during those times. Only nine percent actually had a thermometer in their refrigerator, possibly indicating that some of those who stated that they had one in the previous study were confusing it with the temperature dial. Although there were leftovers in almost all refrigerators, they were dated in only two of those refrigerators. Moldy, spoiled, or outdated foods were found in 24 percent of the refrigerators, and circumstances that might allow cross-contamination were observed in 39 percent of the refrigerators.
Data suggest that circumstances that increase the risk of contracting a food-borne illness do exist in many homes.
The Agency will use this information in developing food safety education materials and programs to arm consumers with the information needed to keep food safety and prevent contamination of food in the home.
The primary objectives of the study were: 1) to determine the effect of contaminated environment on incoming pullets - when do pullets get infected after introduction based on fecal (manure) and organ (dead and culled birds) culture; 2) to determine the shedding rate of S. enteritidis in feces and eggs - quantitative and qualitative analysis; 3) to determine the duration of S. enteritidis shedding in the flock once infected as monitored through regular culturing (manure, organs, and eggs) - qualitative and quantitative analysis; 4) to determine the prevalence of S. enteritidis in resident feral animals(rodents) and house flies (quantitative and qualitative analysis); 5) to correlate S. enteritidis isolations in the environment, chicken organs, eggs, and rodent tissues; 6) to assess the dynamics of molting in the flock and its effect on the presence, shedding and spread of S. enteritidis in the flock - as determined by culture (manure, tissues and eggs); 7) to assess all risk factors to identify the best indicator for the presence of S. enteritidis in eggs and the layer flock environment which can be used for the development of control and prevention strategies on the farm that prevent the transmission of S. enteritidis and ultimately, to reduce the incidence of S. enteritidis illness in humans.
Field and laboratory studies were to be used to determine the prevalence of S. enteritidis on two previously known S. enteritidis infected farms (Flock 1and Flock 2) and on a previously known S. enteritidis negative farm (Flock 3). The project was started on August 17, 2001, with the first samples arriving at the laboratory from Farm 1 on October 1, 2002. Sampling from Farm 2 was started on October 8, 2002, and on May 3, 2002 from Farm 3. Unfortunately, there have been 2 major setbacks during the study period due to Avian Influenza and Exotic Newcastle Disease (END) outbreaks in southern California. The later outbreak has forced us to suspend the project indefinitely. The Avian influenza outbreak started on January 21, 2002. Flocks 1 and 2 were not visited between the ages of 17 and 23 (for a period of 6 weeks) for biosecurity reasons and the field personnel were diverted to help to control the disease in the state. The END virus was diagnosed in this laboratory in early October of 2002 and it has resulted in the complete suspension of the project. The END outbreak resulted in the P.I. being designated as the Laboratory Coordinator to the Federal/State END Task Force, and the diversion of the laboratory, field personnel and the laboratory facility to the eradication effort. Quarantine measures restricted the movement of poultry and other avian stock within the quarantine area and stringent biosecurity measures were put into effect on poultry farms.
Heat inactivation studies under laboratory conditions have been conducted to determine thermal resistance of E. Coli O157:H7, Salmonella spp., and L. monocytogenes in various food products. The data cannot be validated under actual plant manufacturing conditions since it is undesirable to conduct inoculated pack studies in a processing facility using pathogenic bacteria. Thus, development of surrogates can play an important role as biological indicators in validating adequacy of various thermal-based processes.
The objective of this study was to find a non-pathogenic organism with the same z-values and similar or higher D-values than the pathogenic counterparts to serve as surrogate organisms for in-plant inoculated studies in order to evaluate their utility for validating heat processes in inoculated pack studies. D values and z values are measures of the thermal inactivation properties of a given agent and reflect the relationship between cooking temperature and time on death or inactivation of agents such as bacteria or toxins. More than 400 organisms have been isolated from natural sources (e.g., foods, fruits, vegetables, and environment). From those, 50 have been tested to determine thermal inactivation kinetics (D and z values).
Preliminary results with four organisms showed values close to the target parameters. Several pasteurization trials were performed to validate these results, but a greater than expected reduction in population counts was observed, showing a loss of thermo-resistance. Several attempts to assure reproducibility and recover the initial thermo-resistance of those organisms have been unsuccessful. Other strains are being evaluated in hopes of identifying a potential surrogate. After a surrogate is identified, the next step will be to verify reproducibility, test the organism under high-temperature, short-time (HTST) conditions, and validate utility of the surrogate in a juice processing plant.
The Agency hopes to identify a surrogate that can be used to validate the adequacy of thermal-based processes in preventing contamination and foodborne illnesses associated with the contamination. The information will also be used to develop preventive measures programs and recommendations for use by stakeholders to ensure their products are free from pathogenic contamination.
In fiscal year 2001, six (6) grants totaling approximately $800,000 were funded:
What Have We Learned and Are We Closer to Eliminating and Reducing Illnesses?
The transmissible spongiform encephalopathies (TSEs) include a number of animal diseases [Scrapie (which affects sheep), bovine spongiform encephalopathy (BSE), and chronic wasting disease (CWD) in deer and elk] and human diseases (Creutzfeldt-Jakob disease, Gerstmann-Straussler-Sheinkers syndrome, Fatal Familial Insomnia, and Kuru). The animal diseases have typically been thought to be infectious. The human diseases are generally familial in nature with an incidence of about one per million. However, recently, there have been a variety of reports of transmission of the animal disease to humans, with the suspected route of transmission through contaminated food.
Two types of sensors for prion detection are being developed. The first is a cell-based sensor that would be sensitive to infectious prions and other proteins with amyloid structure, and the second is a nanoparticle-based sensor that would be selective specifically to prions, but may not easily discriminate between infectious and non-infectious materials.
Work to improve robustness of the cell-based sensor method, improve reproducibility, explore the limits of sensitivity, and ensure that all prion mimics and infectious prions result in similar cell-sensor response is ongoing. Work to increase the sensitivity, to increase the approach to equilibrium, and to confirm the reproducibility of the antibody-based sensor for prion detection is ongoing.
Work continues on developing a nanoparticle-based sensor for prion detection. Together these two regulatory tools will provide a means for detecting BSE in products regulated by the FDA's Center for Food Safety and Applied Nutrition. These tools are critical to support food surveillance programs designed to keep BSE and other TSEs out of U.S. foods, cosmetics, and dietary supplements.
Project cancelled.
Project cancelled.
The ultimate goal of this 3-year study is to develop a series of transfer coefficients for Listeria monocytogenes during hand and mechanical slicing of delicatessen meats and cheeses with Listeria transfer being dependent on product composition, temperature, compression force, surface tension, and knife and cutting board composition (e.g., stainless steel, plastic, wood, Teflon), with the formation of biofilms and with Listeria's physiological state (e.g., planktonic, agar, or membrane culture, and healthy, stressed, or injured) further impacting the transfer rate. Initially, three sampling devices, i.e., environmental sponge (ES), cotton swab (CS), and 1-ply cotton tissue (CT), were evaluated for quantitative recovery of L. monocytogenes from 304-grade stainless steel surfaces. Recovery was 10-fold greater using CT compared to ES and CS. In our next study, blocks of Cheddar cheese and smoked turkey breast were inoculated with L. monocytogenes. Inoculated product (3 replicates) was sliced (5 slices/replicate) at 4-7° C on a modified commercial delicatessen slicer while applying 2 and 10 lbs. of force. Five product contact areas on the slicer were identified based on Glo-Germ®. They were the table, back plate, metal guard, blade, and product collection area. All product contact areas were sampled using a newly developed CT method. Using an application force of 2 lbs on turkey breast, greatest transfer was found on the metal guard and blade with Listeria transfer 10-fold higher using an application force of 10 lbs. Unlike turkey breast, Cheddar cheese transfer levels were highest on the collection area and blade with the table yielding little or no transfer.
The Agency will use these data to calculate and determine the likelihood of cross-contamination between foods marketed within retail food establishments and delicatessens and will be used to refine current risk assessment strategies.
The microbiological quality of water used to irrigate crops may contribute to foodborne illness associated with the consumption of raw or minimally processed fruits and vegetables. In the study, water samples were tested for the prevalence of Enterobacteriaceae and for the target pathogens E. Coli O157:H7, Salmonella, and Shigella. Enterobacteriaceae in sufficient numbers may result in foodborne illness when ingested.
This approach provides a more comprehensive assessment of the microbial quality of irrigation water. The impact of spray irrigation on contamination of crops in the field is determined. Twelve farms in the southern part of New Jersey are participating in the project. Water samples have been collected from those farms that use well, pond, and river water for irrigation. Salmonella was not detected following microbiological screening of water samples. A variety of Enterobacteriaceae was found. The microbiological quality of farm well water was good, with few bacteria isolated. Based on results, additional farms using lake, stream, or river water were added and the number of farms in the study that use well water were reduced. Laboratory studies using farm collected irrigation water suggest that the microbial load of the water has little influence on transfer to and survival of target pathogens on plant tissue. However, a dose response effect was noted for populations of E. Coli O157:H7 recovered after spray irrigation. Ultimately, the greater the number of E. Coli O157:H7 in the water, the greater the number of the target pathogen on the plant.
Laboratory spray irrigation experiments were conducted using hydroponically and soil grown plants. Review of the literature suggests that many studies are conducted using hydroponically grown plants. Plant maturity, seedling compared to plant >30 d old, was also investigated as a potential variable in bacteria-plant interaction. This study was conducted to determine whether a real difference exits with respect to transfer or adherence between soil and hydroponically grown plants. Results suggest that differences in adherence of the target pathogen appear to exist between seedlings and mature plants.
E. Coli O157:H7 was suspended in farm water, municipal water, and the water used for spray irrigation to determine influence of microbial load on lettuce. The transfer of Salmonella to tomato plants through spray irrigation was investigated. Tomatoes harvested from spray-exposed, hydroponically grown plants were positive for Salmonella. Microbiological quality of farm waters will be tested from April through September 2003 to determine seasonal and year-to-year variation.
A detailed understanding of the potential risks associated with the irrigation of produce will provide the foundation for formulating guidance on safe and appropriate agricultural irrigation practices to prevent contamination of field crops and foodborne illness that could result from use of contaminated irrigation water.
The goal of this project is to provide guidelines to minimize produce contamination by enteric pathogens during production. In addition, Clostridium perfringens is being evaluated as an indicator of fecal contamination of produce. The current project focused on the fate of pathogens on the crop, which is dependent on the climate (temperature, humidity, and rainfall), the type of microorganism, and the type of crop. The specific goals include: (1) Development of irrigation and pesticide application practices which minimize produce contamination by enteric pathogens, (2) development of a predictive model for persistence of enteric pathogens on produce and in soil under field conditions (pre-harvest), (3) evaluation of C. perfringens as an indicator of microbial quality of produce, and (4) establishment of indicator/pathogen standards based on quantitative microbial risk assessment for irrigation waters used in produce production.
Greenhouse preparation and growth chamber construction have been successfully completed. Cantaloupe and lettuce experiments in the greenhouse and in the growth chamber were completed. The preliminary data analyses indicate the following:
At present, the third phase of the growth chamber and greenhouse experiments is underway with bell peppers. A series of field experiments with cantaloupe, lettuce, and bell peppers are in preparation.
In fiscal year 2002, seven (7) grants totaling approximately $1,180,000 were funded:
What Do We Hope to Learn?
No nationwide food system can deliver a risk-free food supply. However a well-conceived strategic approach that quickly and accurately identifies hazards, ranks them by level of importance, and identifies approaches that have the greatest impact on reducing hazards would help support FDA's science-based policies that seek to maximize food safety and public health protection. The objective of this project is to develop a risk-ranking framework that assists in evaluating microbiological, toxicological, and chemical threats that occur intentionally or unintentionally to FDA-regulated foods. A quantitative framework will be developed that includes one or more quantitative models to comparatively rank food safety threats and to evaluate the impact of control measures and practices. Use of the framework will help the Agency achieve its goals of ensuring the integrity of foods, reducing the incidence of foodborne illness, and prioritizing the commitment of Agency resources.
The goal of this project is development of multi-analyte assays for the simultaneous detection of bacterial, viral, and protozoan pathogens, toxins, and allergens in a variety of food matrices. The three-stage approach planned for the research project includes: (1) Developing individual assays, (2) developing sample preparation techniques for selected food matrices and optimizing assays using spiked food samples, and (3) incorporating assays into the multi-analyte format and optimizing conditions of analysis for the analytes relative to appropriate food matrices. Development and use of this assay will permit the Agency to test for and detect multiple pathogens, toxins, and allergens simultaneously instead of using separate tests for each and will provide a new analytical methodology which are designed to identify and avoid possible hazardous substances in the food supply.
The goal of this research is to develop novel optical affinity biosensor technology enabling fast, sensitive, specific detection and identification of foodborne pathogens and toxins in food samples. The research includes: (1) Development of novel optical multi-sensor hardware, (2) development of biomolecular coatings recognizing targeted foodborne pathogens and toxins, and (3) development of methodology for sensor-based detection of foodborne pathogens and toxins in complex food matrices. Development of new detection methodology is critical to the Agency's food surveillance programs, which are designed to keep hazardous substances out of the food supply.
The objective of this research is to characterize the risk from Clostridium botulinum or Bacillus anthracis in dairy products receiving more than one heat treatment. The sporicidal effect of multiple heat treatments on C. botulinum or B. anthracis will be determined in thermal death tube studies as well as during the production of dairy products under laboratory scale conditions using Bacillus cereus as the surrogate testing organism. Results of this research should provide valuable data regarding the potential risks of dairy products in the event of their contamination with pathogenic sporeformers.
The Agency will use this information to develop guidance and provide information to its stakeholders on possible preventive measures that could be taken to ensure the safety of dairy products.
This project intends to validate the use of the applicant's web-based structural database of allergenic proteins (SDAP) to predict possible cross-reactions among food allergens, and to establish a quantitative index to evaluate the potential allergenicity of novel proteins. This research should lead to the development of rapid methods for evaluation of potential food allergens and validation of the methods.
The objective of the project is the development of a nonpathogenic yeast prion protein as a surrogate TSE infectious agent. The surrogate will be used to facilitate a study of the enzymatic degradative process of a disease-causing prion that has been observed in association with a bacterial keratinase produced by Bacillus licheniforms strain PWD-1. This research will provide the critical knowledge needed for reliably measuring the efficacy of treatments or manufacturing processes intended to inactivate the infectivity and biological activity of TSE-related prions.
Surrogate agents for the prion protein associated with TSE diseases will be needed to facilitate research assessing the efficacy of inactivating TSE infectious agents during decontamination/deactivation procedures. The overall goals of this project are: (1) To identify heat- and protease-resistant protein markers that can be used as surrogate agents for prion proteins, and (2) to study denaturation of the protein markers as monitored by monoclonal antibody immunoassays for verifying the efficacy of manufacturing process to inactivate infectious TSE agents. Correlation between denaturation of protein markers and deactivation of prion proteins will be established, and reliability of the immunoassays for predicting deactivation of prion proteins will be evaluated using an in vitro amplification and cell culture model. This research will provide critical knowledge needed to accurately predict the efficacy of prion-targeted inactivation methods in the context of FDA-regulated foods, food additives, dietary supplement, or cosmetics, or the equipment used to manufacture or process them.
Godwin, Sandria L., Speller-Henderson, Leslie, Coppings, Richard J. and Pearson, Lou. 2002. Focus Groups Identify Consumer Differences And Misconceptions Regarding Home Refrigeration Knowledge And Practices. Presented at the 2002 Annual Meeting of the American Association of Family and Consumer Sciences. Dallas, TX. Abstract available through AAFCS Research Abstracts Beth Wuest, Editor. for purchase at http://aafcs.org/abstracts/abstracts.html#O5
Godwin, Sandria L., Speller-Henderson, Leslie and Chen, Furchi. 2003. Refrigeration Practices Among Consumers of Three Ethnic Groups. Presented at 13th Biennial Research Symposium, Association of Research Directors. Program and Abstracts. p. 174. Atlanta, GA. Available at http://www.tnstate.edu/carp/ardabstracts2003/posters2/P129.htm
Godwin, Sandria L., Coppings, Richard J., and Speller-Henderson, Leslie. 2002. A Comparison of Food Refrigeration Knowledge and Practices of Consumers by a Self-reported Food Safety Category. Presented at Thinking Globally Working Locally: A Conference on Food Safety Education, Orlando, Florida, September 17-20.
Smith, MA, Brackett, R.E. , McClure, H.M., Raybourne, R. and Doyle, M.P.. Primates as a model for L. monocytogenes infective dose: A progress report, extended abstract from an invited talk for ILSI-sponsored symposium on Listeria monocytogenes: Current Issues and Concerns--Session I: Pathology, Virulence, and Risk Assessment of L. monocytogenes, International Association for Food Protection, 87th Annual Meeting in Atlanta, GA, August, 2000.
Chappell, C.L., Okhuysen, P.C. and White, A.C., Jr. Cryptosporidium parvum: Infectivity, Pathogenesis and the Host-Parasite Relationship. In Cryptosporidium: From Molecules to Disease. Elsevier Science. (in press).
Chappell C.L., Okhuysen P.C. 2002. Cryptosporidiosis In: North American Parasitic Zoonoses, Richardson D.J., and Krause P.J. (eds.), Kluwer Academic Publishers, Norwell, Massachusetts, pp 113-128.
Okhuysen, PC and White, AC. Parasites in Traveler's Diarrhea Textbook. HL DuPont, Ed., Becker (in press).
Akiyoshi, D., Mor, S., Pearson, D., Tzipori, S. 2003. Rapid displacement of C. parvum type 1 by type 2 in mixed infections of piglets Infect immun. (in press).
Alcantara CA, Steiner T, Barret L, Guerrant RL, Yang CH, Lima A, Chappell CL,Okhuysen PC, White AC. IL-8, TNF -a and lactoferrin in immunocompetent hosts with experimental and Brazilian children with acquired cryptosporidiosis. Am J Trop Med Hyg. 2003, 68:3 325-328.
Beuchat, L. R., T. E. Ward and C. A. Pettigrew. 2001. Comparison of chlorine and a prototype produce wash product for effectiveness in killing Salmonella and Escherichia coli O157:H7 on alfalfa seeds. J. Food Prot. 64:152-158.
Beuchat, L. R. 2002. Ecological factors influencing survival and growth of human pathogens on raw fruits and vegetables. Microbes Infect. 4:413-423.
Buck, J. W., R. R. Walcott and L. R. Beuchat. 2003. Contamination of food crops with human pathogens. Plant Health Prog. doi:10.1094/PHP-2003-0121-01-RV.
Chappell, C.L. and Okhuysen, P.C. 2002. Cryptosporidiosis. Current Opinion in Infectious Diseases 15:523
Huang K., Akyioshi, D., Feng, X., Tzipori, S. 2003. Development of patent infection in immunosuppressed C57BL/6N mice with a single Cryptosporidium meleagridis oocyst. J. Parasitol. (in press).
Kim, C., Y.-C. Hung, R. E. Brackett. 2000. Rules of oxidation-reduction potential in electrolyzed oxidizing and chemically modified water for the inactivation of food-related pathogens. J. Food Prot. 63:19-24.
Kim, C., Y.-C. Hung and R. E. Brackett. 2000. Efficacy of electrolyzed oxidizing (EO) and chemically modified water on different types of foodborne pathogens. Int. J. Food Micro. 61:199-207.
Kim, C., Y.-C. Hung, R. E. Brackett and C.-Y. Lin. 2003. Efficacy of electrolyzed water in inactivating Salmonella on alfalfa seeds and sprouts. J. Food Prot. 66:208-214.
Kudva, I. T., P. S. Evans, N. T. Perna, T. J. Barrett, G. J. DeCastro, F. M. Ausubel, F. R. Blattner and S. B. Calderwood. Polymorphic Amplified Typing Sequences provide a novel approach to Escherichia coli O157:H7 strain typing. J. Clin. Microbiol. 2002 April; 40(4):1152-1159.
Kudva, I. T., P. S. Evans, N. T. Perna, T. J. Barrett, F. M. Ausubel, F. R. Blattner and S. B. Calderwood. Strains of Escherichia coli O157:H7 differ primarily by insertions or deletions, not single-nucleotide polymorphisms. J. Bacteriol. 2002 Apr; 184(7):1873-1879.
Lathem, W.W., Bergsbaken, T., Witowski, S.E., Perna, N. T. and Welch, R. A.. Acquisition of stcE, a C1 esterase inhibitor-specific metalloprotease, during the evolution of Escherichia coli O157:H7. Accepted for publication in Journal of Infectious Diseases, 2003.
Li-Cohen, A.E., and C.M. Bruhn. 2002. Safety of consumer handling of fresh produce from the time of purchase to the plate: A comprehensive consumer survey. J. Food Prot. 65:1287-1296.
Lin, C.-M., S. S. Moon, M. P. Doyle, and K. H. McWatters. 2002. Inactivation of Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis, and Listeria monocytogenes on lettuce by hydrogen peroxide and lactic acid and by hydrogen peroxide with mild heat. J. Food Prot. 65:1215-1220.
McWatters, K. H., M. S. Chinnan, S. L. Walker, M. P. Doyle, and C.-M. Lin. 2002. Consumer acceptance of fresh-cut iceberg lettuce treated with 2% hydrogen peroxide and mild heat. J. Food Prot. 65:1221-1226.
McWatters, K. H., M. P. Doyle, S. L. Walker, A. P. Rimal, and K. Venkitanarayanan. 2002. Consumer acceptance of raw apples treated with an antibacterial solution designed for home use. J. Food Prot. 65:106-110.
McWatters, K. H., I. B. Hashim, S. L. Walker, M. P. Doyle and A. P. Rimal. 2002. Acceptability of lettuce treated with a lactic acid and hydrogen peroxide antibacterial solution. J. Food Quality 25:223-242.
Messner, M., Chappell, C.L., and Okhuysen, P.C. 2001. Risk assessment for Cryptosporidium: A hierarchical Bayesian analysis of human dose-response data. Water Research 35:3934-3940.
Perna, Nicole T., Glasner, Jeremy D., Evans, Peter S., Sandau, Ursula, Soni, Pritin, Shao, Ying, Cebula, Thomas A., and Blattner, Frederick R.. Distribution of island polymorphisms in 180 pathogenic E.coli genomes ; a PCR-based population survey in preparation for Aug 30 submission to Infection and Immunity
Padda, R.S., Tsai, A., Chappell, C.L., Okhuysen, P.C. 2002. Molecular cloning and analysis of the Cryptosporidium parvum aminopeptidase N gene. International Journal for Parasitology 32:187-197.
Park, C.-M., Y.-C. Hung, M.P. Doyle, G.O.I. Ezeike and C. Kim. 2001. Pathogen reduction and quality of lettuce treated with electrolyzed oxidizing and acidified chlorinated water. J. Food Sci. 69(6): 1368-1372.
Park, C. M., P. J. Taormina and L. R. Beuchat. 2000. Efficacy of allyl isothiocyanate in killing enteropathogenic Escherichia coli O157:H7 on alfalfa seeds. Int. J. Food Microbiol. 56:13-20.
Parnell, T.L. and L.J. Harris. 2003. Reducing Salmonella on apples using wash practices commonly used by consumers. Journal of Food Protection. 66:741-747.
Okhuysen P.C., Robinson P., Nguyen M.T., Nannini E.C., Lewis D.E., Lahoti S., Chappell, C.L., Shahab I., and White, Jr, A.C. 2001. The jejunal cytokine response in patients with AIDS associated cryptosporidiosis during immune reconstitution. AIDS 15:802-804.
Okhuysen, P.C., and Chappell, C.L. 2002. Cryptosporidium virulence determinants - are we there yet? International Journal of Parasitology 32:517-525.
Okhuysen, P.C., Rich, S.M., Chappell, C.L., Grimes, K., Widmer, G., Feng, X., and Tzipori, S. 2002. Infectivity of a Cryptosporidium parvum isolate of cervine origin for healthy adults and gamma interferon- knockout mice. Journal of Infectious Diseases 185:1320-1325.
Rich, S., Okhuysen P.C., Tzipori, S. Dynamics of Cryptosporidium parvum Type-2 infection in IFNy-knockout (KGO) mice. J. Parasitology (in press).
Robinson, P., Okhuysen, P.C., Chappell, C.L., Lewis, D.E., Shahab, I., Lahoti, S., and White, A.C., Jr. 2001. Expression of IL-15 and IL-4 IFN-gamma-independent control of experimental human Cryptosporidium parvum infection. Cytokine 15:39-46
Robinson, P., Okhuysen, P.C., Chappell, C.L., Weinstock, J., Lewis, D., Actor, J.K., and White, A.C., Jr. Elevated jejunal substance P expression in AIDS patients with chronic cryptosporidiosis. Journal of Infectious Diseases (in press).
Sathyanarayanan L. and Y Ortega 2003. Effects of pesticides on sporulation and viability of Cyclospora cayetanensis and Cryptosporidium parvum. Journal of Food Protection. Submitted
Sathyanarayanan L. and Y Ortega 2003. Effects of Temperature and Different Food Matrices on Sporulation and Viability of Cyclospora cayetanensis. Journal of Food Protection. Submitted
Smith, MA, K Takeuchi, RE Brackett, HM McClure, R Raybourne, K Williams, US Babu, GO Ware, JR Broderson, and MP Doyle. 2003. A nonhuman primate model for Listeria monocytogenes-induced stillbirths. Infection and Immunity 71(3):1574-1579.
Taormina, P. J. and L. R. Beuchat. 1999. Comparison of chemical treatments to eliminate enterohemorrhagic Escherichia coli O157:H7 on alfalfa seed. J. Food Prot. 62:318-324.
Taormina, P. J. and L. R. Beuchat. 1999. Behavior of enterohemorrhagic Escherichia coli O157:H7 on alfalfa sprouts during the sprouting process as influenced by treatment with various chemicals. J. Food Prot. 62:850-856.
Taormina, P. J., L. R. Beuchat and L. M. Slutsker. 1999. Infections associated with eating seed sprouts: An international concern. Emerg. Infect. Dis. 62:626-634.
Taylor, D. E., M. Rooker, M. Keelan, L.-K. Ng, I. Martin, N. T. Perna, V. Burland, F. R. Blattner. Genomic variability of O-islands encoding tellurite resistance in enterohemorrhagic Escherichia coli O157:H7 isolates. J. Bacteriol. 2002 Sept; 184(17): 4690-8.
Teunis, P.F.M., Chappell, C.L. and Okhuysen, P.C. 2002. Cryptosporidium dose response studies: variation between isolates. Risk Analysis 22:175-183.
Teunis, P.F.M., Chappell, C.L. and Okhuysen, P.C. Cryptosporidium dose response studies: variation between hosts. Risk Analysis 22:475-485.
Venkitanarayanan, K.S., C.-M. Lin, H. Bailey, and M. P. Doyle. 2002. Inactivation of Escherichia coli O157:H7, Salmonella Enteritidis, and Listeria monocytogenes on apples, oranges and tomatoes by lactic acid with hydrogen peroxide. J. Food Prot. 65:100-105.
Weissinger, W. R. and L. R. Beuchat. 2000. Comparison of aqueous chemical treatments to eliminate Salmonella on alfalfa seeds. J. Food Prot. 63:1475-1482.
Weissinger, W. R., K. H. McWatters, and L. R. Beuchat. 2001. Evaluation of volatile chemical treatments for lethality to Salmonellaon alfalfa seeds and sprouts. J. Food Prot. 64:442-450.
For additional information please visit CFSAN's website at http://www.cfsan.fda.gov/.
