Food Safety Applications of Flow-Through Imaging Cytometry

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Although conventional flow cytometry can be used to rapid presence/absence testing for Salmonella in complex foods, it is typically not capable of more nuanced tasks, such as probing the phenotypic complexity of the microbes present or determining the physical interactions of Salmonella with these microbes, or with food debris. We have combined rapid Fluorescence In Situ Hybridization-based labeling of Salmonella spp. in alfalfa sprout washes with flow-through imaging cytometry (FT-IC), using the ImageStream® 100, a commercial FT-IC instrument. This approach enables image-based characterization of various subpopulations of interest occurring within samples of this food. We demonstrate the ability of FT-IC to unambiguously identify cells, cell aggregates and other events within these subpopulations based on both cell morphology and hybridization status after reaction with a Salmonella-targeted probe cocktail. Our ability to directly explore the nature of these events expands the layers of information possible from cytometric analyses of these complex samples and clearly demonstrates that “a picture is worth a thousand dots”.