AUTHOR=Williams Anna J. , Cooper Willie M. , Ramsaroop Shawn , Alusta Pierre , Buzatu Dan A. , Wilkes Jon G. 

TITLE=Rapid Flow Cytometry Detection of a Single Viable Escherichia coli O157:H7 Cell in Raw Spinach Using a Simplified Sample Preparation Technique

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.01493

DOI=10.3389/fmicb.2017.01493

ISSN=1664-302X

ABSTRACT=<p>Very low cell count detection of <italic>Escherichia coli</italic> O157:H7 in foods is critical, since an infective dose for this pathogen may be only 10 cells, and fewer still for vulnerable populations. A flow cytometer is able to detect and count individual cells of a target bacterium, in this case <italic>E. coli</italic> O157:H7. The challenge is to find the single cell in a complex matrix like raw spinach. To find that cell requires growing it as quickly as possible to a number sufficiently in excess of matrix background that identification is certain. The experimental design for this work was that of a U.S. Food and Drug Administration (FDA) In-House Level 3 validation executed in the technology’s originating laboratory. Using non-selective enrichment broth, 6.5 h incubation at 42°C, centrifugation for target cell concentration, and a highly selective <italic>E. coli</italic> O157 fluorescent antibody tag, the cytometry method proved more sensitive than a reference regulatory method (<italic>p</italic> = 0.01) for detecting a single target cell, one <italic>E. coli</italic> O157:H7 cell, in 25 g of spinach. It counted that cell’s daughters with at least 38× signal-to-noise ratio, analyzing 25 samples in total-time-to-results of 9 h.</p>