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Pre-harvest reduction of food-borne pathogens in animals and the environment. <P>
Development of methods to detect pathogens in pre-harvest environments and monitor rates of development and transfer of resistance to antibiotics
NON-TECHNICAL SUMMARY: A Development and transfer of fluorquinolone resistance in Campylobacter jejuni contributes to the severity of foodborne disease. A This project examines the mechanisms of development and transfer of fluoroquinolone resistance.
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APPROACH: Modify TaqMan and Allelic Dsicrimination assays (rapid assays developed in our laboratory) for direct use in detection of Campylobacter jejuni and fluoroquinolone resistant C. jejuni in environmental samples. Use these same assays to monitor the rate of acquisition and transfer of fluroquinolone resistance in C, jejuni in animals, humans, and environmental samples. Monitor rates of transfer of fluoroquinolone resistance among Campylobacters and between Campylobacter and other "gut" microorganisms.
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PROGRESS: 2000/10 TO 2006/09<BR>
In response to several recent listeriosis outbreaks related to deli meats, a commercial delicatessen slicer blade inoculated at 108, 106 or 103 Listeria monocytogenes (Lm) CFU/blade was used to determine the direct/sequential Lm transfer rates to uninoculated deli turkey, bologna, salami and ham. Variables included product type (turkey, bologna, salami, ham), composition (fat, moisture) and temperature (4 and 22C), application force, the Lm strains used (strong vs. weak biofilm formers, healthy vs. injured cells) and attachment time (0.5, 6, 24 h) to the blade before slicing. Transfer was greater (P<0.05) from inoculated turkey (108 CFU/cm2) to the five slicer contact areas using an application force of 4.5 as opposed to 0 kg. At 108 CFU/blade, Lm populations decreased to 102 CFU/slice after 30 slices. Results at 105 CFU/blade were similar with Lm counts of 102 CFU/slice after 5 slices and enriched samples generally negative after 27 slices. Using 103 CFU/blade, the first 5 slices typically yielded about 10 CFU/slice by direct plating with subsequent enrichments generally negative after 15 slices. The higher fat and lower moisture content of salami produced a visible fat layer on the blade that prolonged transfer. At 103 CFU/blade, Lm transferred more readily to ham sliced at 22 rather than 4C with transfer out to at least 100 slices observed following enrichment after refrigerated storage. At 106 CFU/blade, strong biofilm-formers transferred more readily (3.62 log CFU) than weak biofilm-formers (3.12 log CFU). Prior cold-shock (4C/2 h) significantly increased subsequent Lm transfer (3.69 log CFU) compared to healthy (3.30 log CFU) and chlorine-injured cells (3.12 log CFU). Significantly greater transfer was also seen after 6 than 24 h of desiccation due to enhanced survival as shown by viability staining. Hence, if cross-contaminated during slicing, those deli meats that allow growth of Lm during prolonged refrigerated storage can pose an increased health risk for certain consumers.
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IMPACT: 2000/10 TO 2006/09<BR>
Our finings related to Listeria transfer during slicing of deli meats are now being used to develop a series of predictive mathematical models that are being used to refine the current USDA/FDA/CDC Listeria risk assessments that will ultimately impact the current "zero tolerance" policy regarding the presence of L. monocytogenes in cooked ready-to-eat foods. In addition, these results have also led to a number of new innovations in deli slicer design that are currently being introduced commercially.