Detection, quantification, and isolation of Escherichia coli O157 by using flow cytometry and fluorescence-activated sorting

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Pathogenic bacteria in irrigation water may attach to vegetables and can cause foodborne diseases. For safe water and food supply, sources of pathogen contamination should be identified and removed. To identify the sources of pathogens, specific detection and isolation of live pathogens is necessary. The objectives of this study were to develop a method to specifically detect and isolate pathogenic bacteria from environmental water samples by using flow cytometry and fluorescence-activated cell sorting (FCM-FACS). We used fluorescence-labeled anti-O157 antibodies to specifically detect E. coli O157 cells. Detected cells were individually sorted and grown in a medium in 96-well plates, and their identities were confirmed as E. coli O157. Even when the proportion of O157 cells in O157/K12 cell mixture was as low as 0.01%, we could specifically detect O157 cells. In addition, we could detect O157 cells present at 10 cells/ml in environmental water samples. Isolated cells can be used to identify their origins by comparing their characteristics to those in known-source E. coli O157 databases.