ARS | Publication request: Predicting the presence of non-O157 Shiga toxin-producing Escherichia coli in ground beef by using molecular tests for Shiga toxins, intimin, and O serogroups

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2012
Publication Date: October 1, 2012
Repository URL: http://handle.nal.usda.gov/10113/56088
Citation: Bosilevac, J.M., Koohmaraie, M. 2012. Predicting the presence of non-O157 Shiga toxin-producing Escherichia coli in ground beef by using molecular tests for Shiga toxins, intimin, and O serogroups. Applied and Environmental Microbiology. 78(19):7152-7155.

Interpretive Summary: E. coli O157:H7 is a Shiga toxin-producing Escherichia coli (STEC) and the STEC most often associated with the severe forms of foodborne disease. However, numerous non-O157 STEC also have been linked to illnesses and outbreaks of disease. A group of six non-O157 STEC have been described by the CDC as the cause of three quarters of non-O157 STEC diseases. For this reason the USDA Food Safety and Inspection Service has announced its intention to consider these six STEC (O26, O45, O103, O111, O121 and O145) as adulterants in certain beef products. Most of the current methods for the detection of these organisms are based on molecular detection of specific genes. We used this approach to predict the presence of adulterant STEC in 3,972 ground beef samples. There were only six non-O157 STEC containing samples in the set, but 183 samples were identified as positive for STEC because the genes were all present in the sample. This system of testing accurately identified two samples that contained the adulterant STEC but failed to identify the four samples that contained the other adulterant STEC. Although this is the best approach for testing for a STEC at present, improved methods with better specificity are needed.

Technical Abstract: When 3,972 ground beef enrichments with 6 confirmed to contain a non-O157 Shiga toxin-producing intimin-positive Escherichia coli isolate were tested for Shiga toxin, intimin, and O group (O26,045, O103, O111, O121, and O145) genes, 183 potential positives and only 2 of the 6 confirmed positives were identified.