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<OL> <LI> Measurement and prediction of raw produce surface microbial concentrations <BR>a) To use an optical imaging system to measure the volume and surface area of several types of raw produce, and to develop statistical relationships between unit weight and surface area or volume <BR>b) To compare the surface microbial concentrations per surface area of several types of raw produce using surface area predictions <LI>Quantitative recovery of bacterial pathogens from environmental sampling media <BR>a) To compare the effect of transport media, storage time and storage temperature on the quantitative recovery of bacterial pathogens, including Listeria monocytogenes and Salmonella spp. <BR>b) To study the effect of direct enrichment and ambient temperature incubation of environmental samples on the quantitative recovery of bacterial pathogens, including Listeria monocytogenes and Salmonella spp. <LI>To determine if sonication can be used to improve the quantitative recovery of bacterial pathogens, including Listeria monocytogenes and Salmonella spp. from food contact surfaces
Non-Technical Summary: The significance of food or environmental sample selection, collection, handling and transport protocols are often underestimated for microbiological sample analysis. The goal of this proposal is to discover ways to optimize sampling protocols to improve the quantitative recovery of microbial pathogens from raw foods and food contact surfaces. <P> Approach: Objective 1a: Measurement and prediction of raw produce surface area and volume. A machine vision system using radial projection technique will be used to measure the surface area and volume of fresh produce. The surface area of each produce unit will be measured in triplicate with the OmniSurface measurement system (CS Technologies, American Fork, UT). Mathematical equations that relate surface area and volume to product weight measurements will be developed. Objective 1b: Determination of raw produce surface microbial concentrations using predicted surface area. For each test produce, we will enumerate microbial concentrations using a surface rinse technique. For each produce type, 10 samples will be weighed and the surface area and volume measured by the optical imaging system. An additional 10 samples will be surface inoculated with E. coli O157:H7. We will report and compare produce surface microbial concentrations as counts per ml rinse, counts per measured cm2, counts per predicted cm2, counts per volume (cm3), counts per g, and counts per fruit/vegetable for both inoculated and uninoculated produce. Objective 2a: Quantitative recovery of bacterial pathogens from environmental sampling media. First we will determine the rate of cell survival of L. monocytogenes and Salmonella spp. in three broth media under various incubation time and temperature combinations, commonly used for transporting and holding environmental samples. Listeria monocytogenes and Salmonella spp. will be separately inoculated into: Dey-Engley (DE) Neutralizing Broth, Neutralizing Buffer and SRK Rinse Solution. Secondly, we will determine if the proportion of L. monocytogenes to L. innocua or L. ivanovii changes during transport media storage under different temperatures and time conditions. Objective 2b: Direct enrichment and incubation of environmental samples to optimize recovery of foodborne pathogens. A cocktail of Salmonella spp. and Listeria monocytogenes cultures will be inoculated into three environmental sampling media (D/E Neutralizing Broth, Neutralizing Buffer, and Letheen Broth) and two enrichment broths to compare the rate of cell survival in environmental sample transport media and in enrichment media. For L. monocytogenes, UVM and Listeria Enrichment Broth will be used and for Salmonella, lactose broth and buffered peptone water will be used as enrichment broths. Pathogen recovery protocols that maintain the highest populations over time will be further evaluated with in-plant samples from 3 chicken or turkey slaughter / first processing plants on 3 separate visits. Objective 3: Quantitative recovery of bacteria from food or food contact surfaces using sonication. L. monocytogenes will be inoculated on to 3 different stainless steel finishes. For each surface texture and inocula incubation time (1 hr or 24 hr) coupons will be subjected to one of these recovery methods: direct contact, swabbing, rinsing, sonication with a direct contact sonic toothbrush, and sonication in a water bath. Selected sampling methods will be further evaluated by observing the coupon surface with a scanning confocal microscope after the recovery analysis.