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<p>The major goal of this project is to demonstrate improved detection of bacterial pathogens in processed lettuce using a novel DEUF sampling procedure that rapidly collects, concentrates and recovers pathogens from large volumes of produce wash water in combination with an AOAC-approved qPCR rapid detection method. This procedure will be used to detect E. coli O157:H7 and L. monocytogenes in produce wash water in a fresh-cut leafy green pilot-scale production facility and a commercial-scale leafy green processing facility.</p>
<p>The objectives to achieve this goal are:</p><p><ol><li> evaluation of the treatment of leafy green wash water with various enzymes that degrade plant cell wall structure to permit faster filtration of larger volumes of wash water by DEUF,</li><li>comparison of the DEUF concentration method with the standard FDA BAM sampling method to detect E. coli O157:H7 and L. monocytogenes in flume water at Michigan State University's fresh-cut leafy green pilot-scale production facility, and</li><li>3) assessment of the DEUF sampling method to detect E. coli O157:H7 and L. monocytogenes at a commercial-scale leafy green processing facility.</li></ol></p>
<p>The methods for the project will include training and direct involvement of academic, field, and industry scientists in project studies, including use of the DEUF concentration method to collect large produce wash water samples to detect E. coli O157:H7 and Listeria monocytogenes. These studies will be performed in the actual environments in which these scientists work. The success of the project will be measured by the ability of the DEUF concentration method to more reliably and accurately detect E. coli O157:H7 and Listeria monocytogenes in produce wash water compared to standard grab samples. Cultural isolation and qPCR detection probabilities of E. coli O157:H7 and L. monocytogenes will be determined in enriched, non-concentrated and DEUF concentrated lettuce wash samples as defined by AOAC. Besides determining detection probability per method, cultural isolation will be used to determine viable detection whereas qPCR will be used to confirm recovery of cells after DEUF concentration. Binary logistic regression will be used to compare the positive qPCR results (Ct values will be analyzed as 1 for any positive samples and 0 for any negative samples) from the concentrated and unconcentrated lettuce wash water samples. Nagelkerke R square, which can range from 0.0 to 1.0, denotes the effect size (the strength of the relationship); stronger associations have values closer to 1.0. Relationships will be considered significant when the P value for the model chi square is <0.05 and the confidence interval for the odds ratio does not include 1.0. Greater odds ratios indicate a higher probability of change in the dependent variable with a change in the independent variable. Statistical significance for all data will be accepted at the 95% confidence level (a < 0.05).</p>