Byron Brehm-Stecher - Flow-through imaging cytometry for characterization of Salmonella subpopulations in alfalfa sprouts, a complex food system.

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      Biotechnol J. 2009 Jun;4(6):880-7.


      We recently developed an approach combining fluorescence in situ   hybridization (FISH) and flow cytometry for detecting low levels   of Salmonella spp. (approximately 10(3) cells/mL sprout wash)   against high levels of naturally occurring sprout flora   (approximately 10(7)-10(8) CFU/g sprouts). Although this "FISH   and flow" approach provided rapid presence/absence testing for   Salmonella in this complex food system, it was not capable of   more nuanced tasks, such as probing the phenotypic complexity of   the microbes present in sprouts or determining the physical   interactions of Salmonella with these microbes, or with sprout   debris. In the present study, we have combined rapid FISH-based   labeling of Salmonella spp. in 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 these samples. Here, 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".

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