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Rapid detection of respiring Escherichia coli O157:H7 in apple juice, milk, and ground beef by flow cytometry
Author(s) -
Yamaguchi Nobuyasu,
Sasada Makoto,
Yamanaka Mio,
Nasu Masao
Publication year - 2003
Publication title -
cytometry part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.316
H-Index - 90
eISSN - 1552-4930
pISSN - 1552-4922
DOI - 10.1002/cyto.a.10045
Subject(s) - flow cytometry , escherichia coli , carrot juice , staining , food science , biology , fluorescein isothiocyanate , microbiology and biotechnology , food microbiology , bacteria , chemistry , enterobacteriaceae , fluorescence , biochemistry , genetics , physics , quantum mechanics , gene
Background Rapid and simple methods to detect viable pathogenic microbes in foods and drinks are required. Flow cytometry was used for the rapid detection of respiring Escherichia coli O157:H7 cells in apple juice, milk, and ground beef. Methods CTC (5‐cyano‐2,3‐ditolyl tetrazolium chloride) was used to estimate the respiratory activity of bacteria. Fluorescein isothiocyanate (FITC)‐labeled anti‐ E. coli O157:H7 direct antibody (FA) was used for the specific detection of target cells. Food samples were inoculated with starved E. coli O157:H7 and E. coli K‐12 cells, and analyzed by both fluorescent microscopy and flow cytometry after double staining with FA and CTC. Results Respiring E. coli O157:H7 cells in food samples showed strong fluorescence of both FA (green) and CTC (red); thus, they could be clearly and specifically distinguished from respiring E. coli K‐12 or inactive cells. A good correlation was achieved in flow cytometric analysis between the numbers of inoculated viable E. coli O157:H7 and those detected in milk and apple juice. The detection threshold for this flow cytometry for E. coli O157:H7 in milk, apple juice, and ground beef was 10 3 cells/ml (milk and apple juice) or 10 3 cells/g (ground beef) of sample when the total bacterial number in the sample was 10 6 cells/ml. Conclusions Respiring E. coli O157:H7 in food samples can be detected specifically within a few hours. Flow cytometry with FA‐CTC double staining can be used to examine food contamination with various pathogenic microbes demonstrating physiologic activity through the use of a suitable fluorescent antibody. Cytometry Part A 54A:27–35, 2003. © 2003 Wiley‐Liss, Inc.