Flow Cytometric Detection of Pathogenic E. coli in Food

Abstract

Abstract E. coli O157:H7 is one of the more important food pathogens, andrapid, quantitative methods to evaluate foods for the presence of this pathogen are needed. This unit provides exactly that: a very much simplified flow cytometric assay for detection of E. coli O157:H7 in a well established vehicle of infection, ground beef. The method uses commercially available FITC‐conjugated specific antibody to this bacterial serotype. Sample preparation and bacterial enrichment procedures are described. Direct and indirect approaches for quantification of the number of bacteria are given. A key feature of the assay is the reduction in time compared with plate‐counting methods; the tradeoff is a slight reduction in sensitivity. Particularly useful is the simultaneous inclusion of a spiked sample to ensure a positive control. In addition, the unit provides hints on sorting the organisms if desired.