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Investigation of Molecular Targets that Identify the Presence of Pathogenic Non-O157 STEC


Non-O157 STEC are an increasing concern to regulators, beef industry and consumers. However,
rapid and reliable detection of this group of organisms is lacking. STEC contain a variety of
virulence factors that may serve as useful markers that allow a more narrowly focused screening
program to be established. The experiments described here focus on determining which virulence
genes are the best targets to meet this end.<P>

Objective: To determine the combination of molecular markers that best indicates the presence of non-O157
STEC in a beef culture enrichment.

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Findings: The virulence genes nleB, nleC, subA and espK correlated with samples that contained Shiga toxin
genes. Culture confirmation performed on Shiga toxin positive enrichments showed that as the number of virulence gene markers detected increased, the proportion of pathogenic STEC isolates recovered increased while the proportion of non-pathogenic STEC isolates recovered decreased.

Wheeler, Tommy Lee; Koohmaraie, Mohammad; Kalchayanand, Norasak; Bosilevac, Joseph; Arthur, Terrance
USDA - Agricultural Research Service
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