Studies on Simultaneous Enrichment and Detection of Escherichia coli O157:H7 during Sample Shipment

The USDA-FSIS has zero tolerance for E. coli O157:H7 in raw ground beef. Currently, FSIS collects samples from beef processing facilities and ships them overnight to regional testing laboratories. Pathogen detection requires robust methods that employ an initial 15-24 h culture enrichment. This study assessed the potential of using the Phi V10nluc phage-based luminescence detection assay during enrichment while the sample is in transit. Parameters including phage concentrations, temperature, and media-to-sample ratios were evaluated. Results in liquid media showed that 1.73 x 10(3) pfu/mL of Phi V10nluc was able to detect 2 CFU in 10 h. The detection of E. coli O157:H7 was further evaluated in kinetic studies using ratios of 1:3, 1:2, and 1:1 ground beef sample to enrichment media, yielding positive results for as little as 2-3 CFU in 325 g ground beef in about 15 h at 37 degrees C. These results suggest that this approach is feasible, allowing the detection of a presumptive positive upon arrival of the sample to the testing lab. As the current cargo hold controlled temperature is required to be 15-25 degrees C, the need for elevated temperature should be easily addressed. If successful, this approach could be expanded to other pathogens and foods.

Automated summary

The USDA-FSIS has zero tolerance for E. coli O157:H7 in raw ground beef and currently collects samples from beef processing facilities for testing. This study assessed the potential of using a phage-based luminescence detection assay during sample transportation, and the results suggest that this approach is feasible.