Purpose: To validate use of an alternative non-proprietary enrichment media to detect E.coli O157:H7 including non-motile strains (NM) with the Atlas EG2 assay in artificially inoculated raw ground beef and raw beef trim samples containing high bacterial background flora.
Methods: Three hundred seventy-five gram test portions of raw ground beef and raw beef trim with > 105 CFU/g bacterial background were inoculated with high and low levels of E. coli O157:H7 and E. coli O157:NM and enriched in Tryptic Soy Broth + 8 mg/l novobiocin and 1.5 g/l dipotassium phosphate (TSBn+dpp). All samples were enriched for 8 - 18 h at 42°C, transferred into Roka G2 Sample Tubes and loaded onto the instrument. The instrument combines target capture, transcription-mediated amplification, and hybridization protection assay. The results of the new method were compared to the FSIS MLG 5.08 reference method.
Results: E. coli O157:H7 and E. coli O157:NM was specifically detected in artificially inoculated 375 g raw ground beef and raw beef trim samples as early as 8 h enrichment in TSBn+dpp media. The new method performed equally compared to the reference method MLG 5.08 determined by POD analysis.
Significance: The Atlas method provides fast and highly accurate detection of pathogenic E. coli O157:H7 and E. coli O157:NM in 375 g raw ground beef and raw beef trim samples with high bacterial background flora enriched in a non-proprietary commercially available media and results were comparable to the FSIS reference method.