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Proceedings Paper

Detection of immunomagnetically captured 4',6-diamidino-2-phenyl-indole (DAPI)-labeled Escherichia coli 0157:H7 by fluorescent microscopic imaging
Author(s): Shu-I Tu; Joseph Uknalis; Deidre Patterson; Andrew G. Gehring
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Paper Abstract

Live cells of E. coliO157:H7 were captured by goat anti-E. coliO157 serum coated on the surface of polystyrene based immunomagnetic beads (IMB). The captured bacteria were labeled by 4',6-diamidino-2-phenylindole (DAPI), a nucleic acid stain, for observation by epifluorescent microscopy. The beads with captured bacteria were then concentrated by magnetic separators. The efficiency of this magnetic concentration step was less than that of using high speed centrifugation. The antibody-captured and IMB-immobilized bacteria were then applied on HF-treated, bovine serum albumin (BSA)-coated microscope slides mounted on an automated stage, and magnetically aligned before fluorescence distribution was measured by a cooled CCD attached to an inverted microscope. Since the beads were concentrated and linearly aligned along the edge of the magnetic field, image capture along the edge for a few field widths was sufficient to account for most of captured bacteria. We applied this approach to determine the bacterial counts in spiked beef hamburger patties. The results showed that after a 6-hour enrichment, sufficient number of the bacteria could be detected from the samples spiked with 1 CFU of E. coliO157:H7 per gram of the hamburger.

Paper Details

Date Published: 12 January 1999
PDF: 9 pages
Proc. SPIE 3544, Pathogen Detection and Remediation for Safe Eating, (12 January 1999); doi: 10.1117/12.335780
Show Author Affiliations
Shu-I Tu, USDA Agricultural Research Service (United States)
Joseph Uknalis, USDA Agricultural Research Service (United States)
Deidre Patterson, USDA Agricultural Research Service (United States)
Andrew G. Gehring, USDA Agricultural Research Service (United States)

Published in SPIE Proceedings Vol. 3544:
Pathogen Detection and Remediation for Safe Eating
Yud-Ren Chen, Editor(s)

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