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P3-57 Development and Application of the Rapidchek CONFIRM Immunomagnetic Separation (IMS) Kit for the Analysis of Non-O157 Shiga Toxin-producing Escherichia coli (STEC) in Raw Beef

Wednesday, August 6, 2014
Exhibit Hall D (Indiana Convention Center)
Mark Muldoon, Romer Labs Technologies, Inc., Newark, DE
Ann Allen, Romer Labs Technologies, Inc., Newark, DE
Jared Clinger, Romer Labs Technologies, Inc., Newark, DE
Mei Lok, Romer Labs Technologies, Inc., Newark, DE
Introduction: Worldwide, E. coli O157:H7 is the most common Shiga toxin-producing E. coli (STEC) associated with human illness. However, non-O157 STEC are becoming increasingly important and recently, the USDA FSIS has begun regulating serogroups O26, O45, O103, O111, O121, and O145 in raw beef as adulterants.  Current methods for non-O157 STEC detection in raw beef are complex and ultimately require bacterial isolation and colony confirmation.  In order to augment this, we have developed and applied immunomagnetic separation (IMS) reagents for the isolation and confirmation of non-O157 STECs from raw beef.

Purpose: The purpose of this study was to develop and apply new IMS reagents for the detection of non-O157 STEC in raw beef. 

Methods: Affinity-purified polyclonal antibodies were developed against E. coli serogroups O26, O45, O103, O111, O121, and O145 and incorporated into IMS reagents.  The IMS reagents were coupled to the USDA-FSIS modified TSB enrichment procedure for non-O157 STECs (MLG 5B.04) and this was followed by plating to both selective and non-selective agars and colony serotyping. This approach was evaluated for target non-O157 STEC recoveries in both mixed culture, where non-target STEC (O157) was present in 1 log excess of the target STEC (3 log), and coupled to non-selective agar plating, as well as in spiked raw beef (3 CFU target STEC/65 g) followed by enrichment and selective agar plating.

Results: In mixed culture experiments, before IMS, 9.4% of 360 colonies were identified as the respective non-O157 STEC whereas after IMS, 99.2% of 840 colonies were identified as the respective non-O157 STEC.  In raw beef enrichments, before IMS, 54.9% out of 360 colonies were identified as the respective non-O157 STEC whereas after IMS, 99.2% out of 420 colonies were identified as the respective non-O157 STEC. 

Significance: Application of the RapidChek CONFIRM IMS to the analysis of non-O157 STECs in raw beef products should streamline both food process and regulatory monitoring.

Back to: Poster Session - Antimicrobials, Meat and Poultry, Microbial Food Spoilage, Seafood, Sanitation, Non-microbial Food Safety, Risk Assessment
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