Observation and relative quantification of cross-contamination within a mock retail delicatessen environment

Ingestion of ready-to-eat deli meats contaminated with foodborne pathogens has been linked to several outbreaks. For this study, a fluorescent compound (FC) was used to observe deli workers in cross-contamination events to visualize and quantify how potential microbial contamination can move within a mock retail deli environment. Twenty-one participants were recruited and were asked to complete a series of steps involving the slicing of deli meats in which one of the meat products was inoculated with the FC. Upon completion, 16 separate areas (5 × 5 cm) per participant were swabbed to quantify the amount of FC present. A standard curve for the FC (based on absorbance at 370 nm) was developed in order to quantify the amount of FC. For each participant, both video and image data were also collected. These data were normalized and reported as percentages of the total amount of FC collected per participant to allow the amount of FC in each area to be compared across participants. Concentrations of FC by area swabbed and participant were highly variable; even so, consistently elevated levels of FC were found on participantsʹ gloves (18%), on the slicerʹs meat grip (16%), the outside wall of the carriage tray (16%) and within the collection area (13%). Video analysis revealed that high-touch areas include the deli meat, deli meat wrapper, deli paper, and plastic bags which comprised 74% (87 of 118 touches) of the total average hand contact frequency per participant. The relationship between frequency of hand contact and % FC on a particular area swabbed was analyzed, and a Pearsonʹs r value of 0.37 was determined indicating a medium-strength, positive correlation. The findings in this study demonstrate that there is variability among participants within a mock retail deli environment, and thus, likely to be similar variability among workers in an actual retail deli environment. In addition, even in the presence of this variability, this study identifies both areas of elevated contamination levels as well as areas of high hand contact within a deli environment. To our knowledge, this is the first study to quantify cross-contamination events using a FC and to identify potential areas of concern with respect to cleaning and sanitizing as well as employee training.