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P1-35 Simultaneous Detection of Major Shiga Toxin-Producing E. coli (STEC) Serotypes in Ground Beef by Immunomagnetic Bead-based Fluorescent Assay

Sunday, July 26, 2015
Exhibit Hall (Oregon Convention Center)
Alan Gutierrez , University of Florida , Gainesville , FL
Jieun Jung , Konkuk University , Seoul , Korea, Republic of (South)
Tyler Austin , University of Florida , Gainesville , FL
Hyun-Dong Paik , Konkuk University , Seoul , Korea, Republic of (South)
Soohyoun Ahn , University of Florida , Gainesville , FL
Introduction: The USDA Food Safety and Inspection Service (FSIS) considers raw beef products contaminated with E. coli O157:H7 and Big 6 Shiga Toxin-producing Escherichia coli (STEC) serotypes including O26, O45, O103, O111, O121 and O145 to be adulterated, and mandates testing of domestic and imported beef for these STEC serotypes in order to mitigate food safety risks associated with these pathogens. It is estimated that STEC causes 176,000 infections each year in the US, and therefore a rapid and simple detection assay that can simultaneously detect the presence of these STEC serotypes is highly desirable.

Purpose: The purpose of this study was to develop an immunomagnetic bead-based assay for the simultaneous detection of E. coli O157:H7 and Big 6 STEC serotypes in ground beef.

Methods: Immunomagnetic beads functionalized with antibodies to target STEC serotypes were loaded into a microplate and used as a bead-based array platform for STEC identification, and the presence of target STEC was determined by measuring fluorescence signal from detection antibodies. Twenty-five grams of each ground beef sample was inoculated individually with target STEC serotypes at concentrations from 100 to 105 CFU/g. The samples were enriched in 225 milliliters of tryptic soy broth and incubated at 37°C. Each sample was collected at different times (6, 9, 12, and 18 h) and tested with the developed assay.

Results: The developed immunoassay could detect target STEC serotypes as low as 2,000 CFU/ml without any enrichment.  The totally assay can be completed within 4 h, and no cross-reactivity was observed. When ground beef samples contaminated with STEC were tested, the assay was able to detect 1 CFU/g of STEC with 9 h enrichment.

Significance: This study demonstrated the developed immunomagnetic bead-based immunofluorescent assay can have great potential to simultaneously detect multiple STEC serotypes in ground beef present at low concentrations.

Back to: Poster Session 1 – Laboratory and Detection Methods, Low-water Activity; Retail and Food Service Safety; Seafood; Communication Outreach and Education; Produce; Food Toxicology; Non-microbial Food Safety; Food Defense; Microbial Food Spoilage
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