Detection of immunomagnetically captured 4',6-diamidino-2-phenyl-indole (DAPI)-labeled Escherichia coli 0157:H7 by fluorescent microscopic imaging

Shu-I Tu; Joseph Uknalis; Deidre Patterson; Andrew G. Gehring

doi:10.1117/12.335780

12 January 1999 Detection of immunomagnetically captured 4',6-diamidino-2-phenyl-indole (DAPI)-labeled Escherichia coli 0157:H7 by fluorescent microscopic imaging

Shu-I Tu, Joseph Uknalis, Deidre Patterson, Andrew G. Gehring

Author Affiliations +

Proceedings Volume 3544, Pathogen Detection and Remediation for Safe Eating; (1999) https://doi.org/10.1117/12.335780
Event: Photonics East (ISAM, VVDC, IEMB), 1998, Boston, MA, United States

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.

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Shu-I Tu, Joseph Uknalis, Deidre Patterson, and Andrew G. Gehring "Detection of immunomagnetically captured 4',6-diamidino-2-phenyl-indole (DAPI)-labeled Escherichia coli 0157:H7 by fluorescent microscopic imaging", Proc. SPIE 3544, Pathogen Detection and Remediation for Safe Eating, (12 January 1999); https://doi.org/10.1117/12.335780

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