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United States Department of Agriculture

Agricultural Research Service

Research Project: Technologies for Detecting and Determining the Bioavailability of Bacterial Toxins

Location: Foodborne Toxin Detection and Prevention

Title: Development of a faster method for detection of Shiga toxin producing E. coli using Tetrahymena thermophila

Authors
item Salvador, Alexandra
item Clotilde, Laurie
item Bernard Iv, Clay
item Carter, John
item Lauzon, Carol
item Crowe, Chris
item Lin, Andrew
item Hartman, Gary
item Lau, David

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 15, 2011
Publication Date: N/A

Technical Abstract: While most STEC outbreaks are caused by E. coli O157, non-O157 STECs are increasingly being implicated. Selective agar for E. coli O157 is commercially available but none detect non-O157 STEC. Currently, regulatory agencies screen for non-O157 STECs by enriching foods overnight, spreading aliquots onto agar plates, and testing colonies by PCR or agglutination assay until a positive colony is recovered. This process can be lengthy (2-21 days). Here we describe the development of a highly selective medium based on expression of Shiga toxin (Stx). Earlier, it was shown that when the protozoan Tetrahymena thermophila are co-cultured with non-STECs, T. thermophila use the bacteria as a food source, but when co-cultured with STECs, T. thermophila are killed after 6 hours. We looked at this difference in vivo using an antibiotic conductive medium developed by commercial partner, Hardy Diagnostics. The antibiotic present in this liquid broth highly induced the production of Stx by STEC, and after a 2 hour co-incubation with T. thermophila, all T. thermophila were killed. As a result, we are currently exploring the development of a biphasic system to identify STEC. This system will be comprised of a thin liquid overlay of T. thermophila on an agar similar in composition to the commercial medium available and selective for E. coli. This system would accelerate identification of STECs, reduce the time to issue a product recall, and could be used by regulatory agencies.

Last Modified: 12/22/2014
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