Evaluation of the GENE-UP® Assay for the Co-Detection of Escherichia coli O157:H7 and Salmonella spp. from Raw Ground Chicken

Introduction: In the US, among the foodborne pathogens, non-typhoidal Salmonella and Escherichia coli O157:H7 (STEC O157) are responsible for an estimated 41,930 and 3,704 laboratory-confirmed episodes of illnesses. Most of the commercially available PCR systems utilize separate systems for the detection of these pathogens. Given the common niche occupied by these pathogens, and the overall similarity in their generation times, it would be useful for testing laboratories to have a common workflow that can be utilized for simultaneous detection of both pathogens. The GENE-UP^™ Salmonella (SLM) and E. coli O157:H7 (ECO) assays are Fluorescence Resonance Energy Transfer (FRET) based real-time PCR that utilize a common workflow, including the sample preparation method.

Purpose:   In this study, we have evaluated the ability of SLM and ECO to detect Salmonella and STEC O157 from a co-inoculated raw ground chicken matrix using the two mostly used enrichment media, BPW and mTSB.

Methods: The 25g raw ground chicken samples were co-inoculated with Salmonella and STEC O157, such that per media, n=20 samples were spiked at a fractional levels (0.25 – 0. 75cfu/test portion), while n=5 samples each were spiked at high levels (>2.5cfu/test portion) and no inoculation, respectively. All analytical outcomes were biochemically confirmed by the traditional reference method (USDA/FSIS MLG 4.09 and 5.09) and by an alternative method; including streaking onto bioMérieux’s chromogenic agar, ASAP^TM for Salmonella and ChromID^TM EHEC for STEC O157.

Results: Statistically equivalent performance (95% CI) were observed upon {dPOD}, where alternative method demonstrated no significant differences between the presumptive and the confirmed results for both Salmonella and STEC O157 per BPW and mTSB [dPOD_cp: 0.0; LCL:-0.28; UCL: 0.28]

Significance: These data demonstrated that the GENE-UP^TM system can be used for co-detection of Salmonella and STEC O157 and the common workflow significantly reduced the workload for laboratory testing personnel and enabled a quicker turnaround of results.