Purpose: The objective of this study was to evaluate the Bio-Rad iQ-Check<sup>®</sup> Real-Time PCR STEC method for the detection of inoculated Shiga toxin-producing Escherichia coli in ground and raw beef trim in comparison to the USDA FSIS MLG 5B.02, 5.06 and 5A.02 methods.
Methods: Portions of ground and beef trim were inoculated individually at low (0.2-2.0 cells/25g) or high (2.0-10 cells/25 g) inoculation levels with 5 different serotypes of E. coli. The 25 g samples were combined with 350 g or 300 g of uninoculated beef for analysis with the iQ-Check and USDA FSIS MLG methods, respectively.
After 10 and 12 h of incubation in a 1:4 dilution of STEC Enrichment Broth, the samples tested with the iQ-Check method were analyzed with the kit for presence of stx and eae genes followed screening for the USDA “Top 7” O groups using the kit if the samples contained stx and eae. The samples tested with the USDA FSIS MLG 5B.02/03 or 5A.02 methods were analyzed with the primer and probe sets as prescribed by the method or with BAX®E. coli O157 MP test. All samples were confirmed for the presence of target STEC organisms regardless of the screening result using the FSIS MLG 5B-02/03 and 5.06 methods.
Results: For inoculated beef trim and ground beef, the commercial method performed statistically as well as the USDA FSIS MLB 5B.02/03, 5.06, and 5A.02 methods for the detection of Shiga toxin-producing E. coli.
Significance: The commercial method provides a commercially available option to detect STEC in beef in as little as 10 h.