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Validation of a Comprehensive Method for Detection, Isolation and Confirmation of All and ‘Top Seven’ O-Serogroups of Shiga toxin-producing Escherichia coli


<p>The goal of the validation is to generate statistically valid data for obtaining official approval of the newly-developed testing scheme by the MMC so that the method can be used in routine testing activities to improve food safety. The method will be evaluated against a reference method(s) as: </p>
<p><ol><li>a method to directly detect all and the ‘Top 7’ O serogroups of STEC in enrichment broth of food samples;</li>
<li>a method to isolate all and the ‘Top 7’ O serogroups of STEC colonies from enrichment broth;</li>
<li>a method to confirm isolated colonies grown on agar or in broth media as STEC or selectively, any one of the ‘Top 7’ O serogroups of Shiga toxin-producing E. coli. </li></ol></p>

<p>The specific objectives include: </p>
<p><ol><li>to evaluate inclusivity and exclusivity,</li>
<li>to test matrix effect,</li>
<li>to determine the limit of detection, and </li>
<li>to conduct inter-lab evaluation.</li></ol></p>

More information

<p>Recent food-borne outbreaks and the new regulation that beef products exported to the USA must be free of the “Top 7” Shiga toxin-producing Escherichia coli (STEC) have triggered a need for improved methods for testing STEC, particularly the “Top 7” STEC, namely O26, O45, O103, O111, O121, O145 and O157. We have developed a comprehensive scheme based on a combination of immunological, PCR and culture assays for detection, isolation and confirmation of the ‘Top 7” or all STEC in food, which is in a ready-to-validate stage. </p>

<p>We propose to validate the method to make it available for regulatory testing. The validation will be conducted following ISO17025 standards and meeting the requirements of Canada’s Microbiological Methods Committee (MMC). We will work with MMC, the E. coli Reference Laboratory (PHAC, Guelph) and Pro-Lab, to ensure the best possible outcome. The method once validated can be used by industry, government and diagnostic laboratories.</p>

Chen, Shu
University of Guelph
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