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Food Safety: Farm to Table

Gilliland, Stanley; Zhang, Glenn
Oklahoma State University
Start date
End date
  1. Determine a minimum number of a selected culture of Lactobacillus acidophilus used as a feed supplement to inhibit Salmonella typhimurium in weaning age swine.
  2. Determine effect of L. acidophilus on the local and systemic immune response in pigs and cattle.
  3. Develop molecularly imprinted polymers to rapidly detect Escherichia coli 0157:H7 in the primary enrichment procedures currently used for detection of this pathogen in foods.
  4. Optimize a fluorescence-based PCR assay for non-gel detection of Listeria monocytogenes in foods.
  5. Determine the influence of variations in gaseous atmosphere during growth on viability, cellular morphology and composition of Campylobacter jejuni.
  6. Develop improved method for recovering Campylobacter jejuni from foods.
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NON-TECHNICAL SUMMARY: A. Microbial food safety is a high priority area not only for processors but for producers of livestock and consumers. Escherichia coli 0157:H7 and Listeria monocytogenes are two food borne pathogens currently causing great problems especially in foods of animal origin. Campylobacter jejuni also is a pathogen of major concern however detection methods for it are inadequate. B. New or improved methods of controlling and detecting these pathogens would greatly enhance our ability to ensure consumers of the safety of the food supply. A. This project investigates the use of probiotics as feed supplement to control foodborne pathogens, such as Escherichia coli 0157H:7 and Salmonella, in livestock during production. B. The project also examines development of new rapid methods of detecting foodborne pathogens in foods.

APPROACH: Lactobacillus acidophilus L-23 isolated in our laboratory will be fed, in different numbers, to weaning age pigs which will then be challenged with a virulent culture of Salmonella typhimurium. The numbers of the pathogen shed in feces of the pigs will be monitored to determine the lowest level of the lactobacilli required to inhibit the salmonella in the pigs. Blood from cattle and pigs fed cells of L. acidophilus will be compared to that of control animals to determine if differences occur in the intensity of immune responses. Biosensors made from molecularly imprinted polymers specific for E. coli 0157:H7 will be tested for rapid detection of the pathogen in enrichment cultures used for conventional methodology in detecting it. This could greatly reduce the time required to detect E. coli 0157:H7 in foods. A commercially available Fluorogenic UniPrimer and primers specific for Listeria monocytogenes will be used to develop a non-gel PCR assay for this organism in foods. Growth of Campylobacter jejuni is greatly influenced by atmospheric conditions under which it is cultivated. Proper conditions are necessary to prevent the organism entering a nonculturable state. Using the conditions thus far developed in our labaratory, we will develop an improved method for recovering the organism from foods. This will greatly enhance the reliability of detection methods for this pathogen.

PROGRESS: 2003/07 TO 2005/06
The percentages of coccoid cells formed by two strains of Campylobacter jejuni was influenced by the atmosphere under which they were grown. When grown in a chamber with modified gaseous atmosphere (Campy-Pak) they formed a lower percentage of coccoid cells than did cultures grown under the conditions recommended in currently recommended methods. The cellular fatty acid profiles of the strains were not related to the amounts of coccoid cells formed. Using tissue culture flasks in a chamber having a gaseous atmosphere of the composition produced by the Campy-Pak, for the enrichment culture in detection of C. jejuni provided more consistent results than were obtained using the method currently recommended by regulatory agencies. A Uniprimer system for a sensitive real time PCR detection of Listeria monocytogenes in meats (raw or processed) has been developed that will detect as low as 1 cfu L. monocytogenes in a 25 g sample. Feeding a probiotic strain of Lactobacillus acidophilus of bovine origin did not influence the overall immune response in young calves. However, the animals were not challenged with any form of stress which may have elicited a difference in response in the form of differences in levels of immunoglobulins in the animals. These studies will be redone in a later project to include a stress in the form of injected lipopolysaccharides to see if the probiotics will cause a more rapid and/or higher level of production of immunoglobulins. Feeding a probiotic to young swine challenged with a culture of salmonella failed to show an effect. This was due to the fact that the challenge did not cause increased growth and/or action of the salmonella in even the control group. However, in a related trial there was a tendency toward increased production of immunoglobulins in swine fed a L. acidophilus. Further experimentation is needed to determine if the probiotic will produce an response in the form of increased immunoglobulin production in swine exposed to a challenge that causes a negative effect in the control animals. Molecular imprinted polymer (MIP) films have been developed that have a binding affinity for Escherichia coli 0157:H7. These will be tested in the next project to determine potential for use in detecting E. coli 0157:H7 in raw ground beef. This will focus on rapidity of detection in an enrichment culture.

IMPACT: 2003/07 TO 2005/06
The over all impact of this project should lead to the production of foods that have less chance of containing food borne pathogens. This will improve consumer protection.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Bacterial Pathogens